The best thing you can do is try to understand the signs and symptoms thoroughly, and know the difference between dystonia and other performance-related injuries in the hopes of getting an accurate diagnosis when things get really bad; especially the difference between focal embouchure dystonia and overuse injury which are often mistaken as the same thing, but they are completely different.
The reason why overuse and embouchure dystonia are often mistaken as one another is because the symptoms during onset are very similar. The key difference is that embouchure dystonia does not elicit pain (yet it does come with a lot of tension/resistance when trying to play).
With overuse injuries a player will usually go through a period of time where they are playing more, have added responsibilities, and they start to see a degradation in their higher register and usually start to exert abnormal pressure to try to hold it together and end up with swelling, pain, tingles, sometimes this leads to other injuries like muscle tears or nerve entrapment. The upper lip or obicularis oris in general starts to feel rubbery, stiff, sometimes there are slight tremors or twitches, and eventually if very bad, no ability to produce a sound occurs. Overuse can sometimes be a result of improper technique or bad habits, but not all the time. It can be as simple as ignoring signals of pain, or not taking them seriously enough and taking improper care. Unfortunately musicians are not taught enough about medical care or preventative care from strain injuries such as how to properly ice/heat pack, stretch, myofascial release, use of guards etc. Usually taking a month or two off from playing, ice packing/heat packing and rest improves things and playing resumes to normal. If it is a result of bad technique/habits, then focusing on those areas will show improvement.
If a secondary injury occurs like a muscle tear or Satchmo's Syndrome, a player will usual feel a striking/jabbing pain in the upper lip that feels somewhat like it's been pierced with a needle. Usually there is a bump/small lump in the upper lip you can only feel when rubbing the inside of the lip with your fingers. It will hurt when playing with the mouthpiece on that area and/or after playing for a short time in the upper register.
Never entrapment will feel similar, but mainly tingles in the upper lip, jaw, or other area of the face, and no noticeable bump or jabbing pain. I don't think this is common. There are some brass players that develop nerve entrapment in the upper lip due to a perturbing incisor tooth digging into the lip and there will be swelling that runs from the bottom of the lip up to the nose on the inside, tingling, sometimes a dullness to the pain. The tooth can be filed down or corrected with braces.
Both nerve entrapment and muscle tear early signs are tingles. If you feel any tingling at all, you need to take time to rest and properly take care of things. Even if you feel the tingles go away a couple hours after playing...it is not good enough to just assume things are getting better, especially if it occurs every time you play and/or on a consistent basis. You need to figure out what you are doing or what is causing the body to signal that something is wrong.
Bell's Palsy is when one side of the face is paralyzed/lacks mobility and the other side doesn't. This is very noticeable right away visually and physically. A player will find it difficult to eat, talk, there will be a noticeable droopiness to the paralyzed side of the face and lack of ability to move anything on that side, especially near the eye. Noticeable drooling, decreased taste, no ability to close or open the eyelid, pain and numbness behind the ear (where the facial nerves branches out from), and sometimes an increased sensitivity to sound; everything seems louder. The paralyzed side will feel extremely weak and sometimes there are twitches that occur.
TMJ - pain in the jaw joint, soreness around the back of the jaw, difficulty chewing or eating due to the pain, popping in the jaw, all of this on one side or both sides of the jaw. Sometimes lock-jaw...meaning difficulty opening or closing the jaw. Pain when trying to open the jaw wider. Sometimes headaches, and sometimes a feeling of unevenness in the jaw closure (teeth don't feel aligned), accidentally biting the tongue or cheeks. In low brass playing sometimes lock jaw. It is common to see TMJ in woodwind players such as clarinetist, sax, etc.
There are several other ailments a musician can encounter that I have not listed here such as tooth infections residing in the jaw, gland infections/mouth stones, other forms of severe nerve compression, other related dystonias like oromandibular dystonia, etc. It helps to educate yourself on the various ailments and trauma that can happen to the upper body and face, and know your anatomy and nerves, etc.
Focal embouchure dystonia onset is hard to recognize and diagnose because the signs and symptoms are very similar to other setbacks. During onset of embouchure dystonia a player will usually be going through a period of time with increased performance responsibilities or working a lot on repetitive practice preparing for something or in an environment where a lot of emphasis is focused on technique. There might be an embouchure change focus too. There are a multitude of things that are known to possibly harbor breeding grounds for dystonia. However, it is without a doubt a multi-faceted neurological disorder that occurs out of the blue and very sneaky to catch.
Like with any other injury/setback, they might be experiencing a lot of stress or taking on a lot of work, but with embouchure dystonia, despite stressors, usually the player is at the height of their playing career or feel their playing is the best it's ever been; things usually feel natural and easy and at peak performance ability. Usually they are late starters, extremely fast learners, high achievers, and not all, but most are are in leadership positions. Though it is not uncommon to see why professionals usually develop the disorder, amateur enthusiast do too and usually hold common characteristics.
During onset there is no pain. Yet a player will notice small things that occur that phantom technical/mechanical issues. For example, there might be a slight air leak in the lower register, or a slight tremble on notes in the lower register that come and go, or troubles with certain interval jumps that usually aren't an issue. There is a feeling of loss of endurance sometimes (not painful, but like can play something one time through, but the second time feeling a lot of resistance while playing and like there's a lot of overshooting notes, missing notes, or not being able to land on notes when doing certain interval jumps).
The common symptoms (yet not everyone develops every single one of these symptoms, so just because you don't have all these symptoms, doesn't mean you should just disregard it...it's usually a combination of any of the following) of embouchure dystonia can be: range-specific (having troubles playing in one register), dynamic specific (having troubles executing decrescendos but not crescendos or vice versa, troubles playing quiet, but not loud or vice versa), articulation-specific (can articulate scales going upwards but not downwards, or vice versa, or no ability to tongue at all, or can articulate at a fast tempo, but not at a slow tempo or vice versa), tempo-specific (can play things fast, but not slow or vice versa). Other signs are lock-jaw in low brass/woodwinds with no pain, aperture clamping (the aperture closing shut randomly while playing or spasming shut), if symptoms are most noticeable in the tongue (inability to articulate passages) or very intense it can carry over to other tasks like drinking out of a water bottle and sometimes speech (tripping on words). Most all, but not everyone, notice a lack of symmetry to the face - not so definite as bell's palsy, but one side of the face will seem less responsive than the other side. Air leaks are common as I stated before too.
Usually the player will increase their practice time or focus on correcting these specific issues with technique, or the opposite, trying to rest, but to find it only made things worse. The symptoms are gradual and they seem to layer on top of one another over time.
For example, I noticed a small air leak in my low register, then later on I noticed I had troubles decrescendoing while doing long tones, my muscles would give way. Then I couldn't do large interval jumps, I had to slur them. Then I had troubles tonguing things in descending passages later on, and when I looked in the mirror, my embouchure would look stable for 5-10 minutes, and the second time I tried to run through a passage, my embouchure started moving a lot all over (looked like I was chewing a wad of bubble gum in my mouth while playing). I started to notice loss of smaller interval control, and after focusing on my lower register studies, it made things worse, and after taking time off, I had uncontrollable and intense spasms and tremors.
Some players will go so far as to continue playing on an unstable embouchure due to performance responsibilities and/or obligations, and this increases a secondary injury factor. Some will develop overuse symptoms on top of their embouchure dystonia symptoms because they are forcing their embouchure to stabilize via pressure or just by continuing in general and result in swelling, etc. and at worse a muscle tear, and possibly TMJ/jaw strain or pain. Even if there is a secondary injury, usually after resolving it, the embouchure dystonia remains. The key difference is that overuse injury/syndrome and other injuries is that they can be prevented and/or cured with rest, medical care, and significant time off. Dystonia will only worsen over time with or without rest, and correcting things will not help either.
You can see why onset is so hard to catch and especially how it can be mistaken as other setbacks during the early stages. Even though we don't know the etiology of embouchure dystonia, we know that it manifests as a neurological disorder. Not only is it neurological, it seems selective, and with that said, it is most likely inevitable. There might be no stopping it even if recognized. Hand dystonia is much easier to catch and has some cases of prevention during onset, whereas embouchure dystonia, not so much.
Even if it was, the embouchure is extremely difficult to navigate while having dystonia and there are few rehabilitation strategies if none that have been documented, tested, or that can be applied in the hopes of prevention.
That is why I document my rehabilitation, because no one else has ever attempted to publicly in history.
It is not realistic nor correct to tell musicians, "Avoid placing yourself in situations where you are playing more than normal, avoid bad technique or bad habits sneaking in, don't use too much tension, and avoid using too much pressure, try to take care of anxiety or nerves, etc. " BECAUSE EMBOUCHURE DYSTONIA IS NOT A RESULT OF BAD HABITS, BAD TECHNIQUE, PRESSURE, BUILT UP TENSION, LACK OF AIR SUPPORT, PERFORMANCE MENTALITY, or whatever else you want to try to re-label it as!!!!! (Sorry, I got a little angry there...but this re-labeling trend is part of the problem and a bigger issue to address in writing later).
By telling musician's to avoid common situations that we are all usually placed in at one point or another, is like telling a musician, "You might as well not try at all. Your safest option is to not play music at all, because you might injure yourself or develop a rare neurological disorder called dystonia."
If you notice a change in your playing and it seems to be of concern, your best bet is to keep a journal (written and/or video) observing your playing and document any changes over time. If you feel like it might be dystonia, focusing on standard technique or repetitive tasks in your playing will degrade you further. Avoid it if can, but even avoidance won't help necessarily. If you can take time away from playing, do so not to rest, but to carefully observe your symptoms and note changes.
If you feel it is embouchure dystonia, then stop playing immediately, remove yourself from your current environment if can, seek out a neurologist who has diagnosed and/or researches embouchure dystonia....though most will not diagnose you during early onset because it is too early to tell, they might (not guaranteed) provide you with some temporary medicine to try tetrabenazine/artane, risperidone, etc. that might provide temporary relief...however, these are used to suppress symptoms, not cure them, and there is no promise it will regress the symptoms. It is important to get tested in order to rule out any other possible ailments in the blood work and brain scans.
Other things you can do is try increasing your dopamine levels through dopamine supplements or anything that might affect serotonin too. You can also try tremor supplements that are not drugs, but nutritional supplements that can be found online. Look for supplements for essential tremors or tremors in general. I do find these have helped me, but again it's not the same for everyone. There's all kinds of alternative holistic therapies and supplements you can try.You can look at my left hand side-bar and it covers several alternative-medicines and therapies.
If you have dystonia, a sensory trick might work. Does touching areas of the face when spasms occur cause the spasms to stop? does placing something between the teeth cause things to stop? (like a cotton ball, mouth guard, etc.).
I also would suggest that if you think it is embouchure dystonia...and even if it is not....you should start implementing stretches in the upper back, neck, jaw, tongue, and face every day. This should already be a part of any routine, but not often taught to students. It helps take away tension from fighting the symptoms.
Sadly there is no preventative measures. Everything that I have suggested here can only aim to possible temporary relief, and/or reduce of symptoms maybe at best.
Like I stated before, educating yourself on signs and symptoms is best and seeking out help when it is time. After you have been diagnosed by a reputable neurologist, seek out a rehabilitation practitioner who aids in the recovery process.