I think the first thing I learned to avoid in the beginning was adding the sauce to the chicken too early. I had to learn to save saucing the chicken until the last few minutes. Otherwise the sugar gets burnt and tastes bitter.
My advice would be you are going to mess up. Mistakes happen. Food will sometimes cook quicker then you want, or take longer, much longer. Relax, we all started somewhere.
Before putting on party, practice a few times the meat you want to cook. Do not try something like a turkey on the smoker for Thanksgiving if you have never done one. Practice. Also, experiment. Try different rubs, different wood. Once you got your rub, injection, wood, flavor down, practice some more. That is the great thing about this. You can practice and enjoy eating the practice attempts.
And some find having a journal helps. Write down everything you did for the cook, take notes.