My company has an upcoming review, and this will be my first under any sort of professionally done process. How do you prepare for them? Anything to watch out for?
Be positive in your reviews and don't complain or be negative, focus on you. Discuss your accomplishments and skills/progress in the context of your groups goals and your overall companies goals. While doing that discuss/remind your boss of what you've done and how you've contributed to these team goals. Ideally, you've done this for the whole year so your review is a summary of what you've already discussed with your manager this year. In practice you've probably not done that so it's hard to provide a comprehensive summary without any notes or previous discussions to reference. So that being said you should focus on your work and your long term career goals in the context of how you can make your bosses job easier/more productive, likewise for the company.