A good practice is to ask people to write as opposed to speak. You can give some space for everyone to put their thoughts on post-it notes before the conversation starts (or to put things in a doc before the retro meeting).

There are so many dimensions: shy v. not, or introverted v. extroverted, or active v. passive thinker, or oral v. written communication, etc. Ideally you shape practices that can account for this diversity of thought.

And +1 to setting expectations so that people who are very vocal don't take up all of the space.