Look into Alexander method that might help with the looking nervous thing.
Btw aa never goes away. You just learn to deal with it. There are some simple exercises you can do to help with it. Tomorrow go to some public place and try to have a casual conversation with 3 strangers. Doesn't matter what about just talk. Make good eye contact and speak to them.
I won't get into it now since I am typing on an iPhone, but there is a idea of preopeners. Things like eye contact and body language that make opening a set better.