What do you do in order to be less anxious or to slow down during or for an interview?

I tend to get anxious before an interview. I speak too fast, stutter on words, and even though I dont think its that noticeable, I know I am not being my best self.

Even in the interview I am aware how I am speaking too fast and try and slow down, but sometimes its too late. What can I do before hand to relax myself?

I had a screening call the other day and the recruiter called without any notice. I did much better on that call because I didnt have time to get worked up before. I was myself the entire time and calm and confident.