For better or worse, non-judicial punishment (NJP) is exactly what the name implies. As authorized by Article 15 of the Uniform Code of Military Justice, a commander may discipline their troop without the need for a court-martial. On the one hand, a commander is keeping things at the lowest level possible and punishments can only be so extreme (depending on the type of NJP, of course). On the other, due process is sidestepped and the judge, jury, and executioner is a single person. But there are a few ways to make sure your Article 15 process goes as smoothly as possible.
Here's what you shouldn't do when getting an Article 15:
Don't think not signing means you're in the clear
It's an embarrassingly common misconception. Some people think that signing an Article 15 is an admission of guilt. It's not. It's just saying that you agree to go down that route. More often than not, depending on the circumstances, you'll want to just take the NJP.
Escalating the hearing to court-martial means that you're putting yourself at risk of confinement and possibly an administrative discharge. If you are facing just a summarized Article 15 (the least severe of NJPs), the most you can get is 14 days of extra duty, 14 days of restriction, and an oral reprimand.
Don't cry for a lawyer
Your civil rights are still a thing when facing a NJP, but it's not always the best course of action to call for a lawyer when the punishment can be kept in house. You are allowed legal representation (if you're not facing the extremely light summarized), but remember, you're not convincing a military judge who has heard many trials.
Instead, you're trying to convince your commander who has long been with you and should (probably) know who you are as a troop by now. You may bring spokesmen, evidence, and witnesses and you should probably let the person who knows the commander best do all the talking.
Don't mouth off to your commander
Now is not the time to pop off with an attitude. If you know with 100% certainty that you are innocent, explain the situation as calmly and soundly as possible. If you know you're guilty and the commander has you dead-to-rights, then don't dig your grave deeper.
Actual judges and justices must hide emotion and let the facts do the talking. Your commander doesn't want the unit to look bad and is doing what they must. The fact that they allowed you to just take an Article 15 instead of automatically going to court-martial means they're at least a little bit on your side.
Don't scoff at the chance of a suspended punishment
Another element unique to an Article 15 is that the commander may suspend the punishment. Meaning, if they choose, a commander can put you on probation without any actions taken against you. This probation can last up to six months and, at the end of those six months, the commander may believe your punishment was paid for with a very stern lecture (if your behavior's been good).
Thank your commander if they give you this option and keep your word when you say, "it'll never happen again." One slip up and your actual punishment begins. This could even happen for something small, like being a minute late to PT formation.
If you feel you were unjustly punished, don't forget to appeal
But let's not give every single commander the benefit of the doubt. We'll admit it; there are bad apples who may drop the hammer for a slight infraction because they hold a grudge against you. You always have the right to appeal the verdict, escalating the issue to the next highest level.
If you appeal within five days, your case will be brought higher. Worst case scenario, your appeal gets denied. If it gets accepted, then the worst case is that your punishment stays the same. You don't really have anything to lose by appealing.
After two years (or you PCS/ETS), don't bring it up again
This final tip is for E-4 and below. After two years (or if you PCS/ETS), an Article 15 is destroyed and can't be used against you.
E-5 and above, unfortunately, have the Article 15 on their record forever (unless you have it expunged). If you messed up as an E-3, took it on the chin like an adult, and now you're thinking of staying in, just keep that embarrassing blemish on an otherwise clean career to yourself and nobody will give a damn.