I freeze in interviews, tips?

I get tongue-tied when I am asked about my weaknesses. There are 12 people counting on me, so I am trying to be careful. I want to come across as confident and honest. How do you prepare answers?

Arrive early, drink water and take a slow breath before you walk in. It sounds simple but it helps.

Thanks for writing this out. I went through something close to it 7 months ago, and it settled down once I kept a simple log of every call and form.