1. Arrive early, but don’t go inside. You can't be late OR too early. So find a coffee shop or restaurant where you can wait, so you won't have to worry. Running late for an interview makes you even more nervous.
2. Stop rehearsing. Practicing for interviews is okay. Just maybe not RIGHT before you go in, because you can end up sounding too scripted. Being conversational is almost always better. So just try to relax and clear your head.
3. Don't put yourself in a position where you have to cram for your interview. You should research the company and know your talking points WELL ahead of time. It's a lot more stressful when you're googling them on your phone in the parking lot.
4. Avoid any excess stress. Which might include things like reading the news or checking your email. If those things help you RELAX, go for it. Just don't do anything that adds to your stress. And as corny as it sounds, thinking happy thoughts really can put you in a better frame of mind.