1) Be humble. Don't expect people to take it easy on you because you got street cred (You are a ruby contributor? You still need to show them how good you are at coding Ruby). Many people with creds get offended when they realize they are not as good as their credentials would imply.
2) Know yourself. Most candidates I've seen, including myself, encounter a moment in the interview where they get hit by the nerves. Know that it's going to happen, announce it to the interviewer, recompose yourself, start again when calmer. You are not going to fail an interview because you are nervous. You will not succeed if you are terrified, panic, and shut up.
3) Explain your reasoning. The way you approach a problem, which is a large part of what the interviewer wants to see is in your mind only unless you vocalize it. With a good enough mental approach, you will get a lot of slack on the actual code by most interviewers.
4) Interview your interviewer. Go prepared with smart, non-trivial questions on the job and the company. Ensure your interviewer is an empathic, intelligent, and humble person. Assume anything annoying you experience is going to be relatively permanent at the job -- will that be acceptable or not?