Try to do some light stuff firstly,
Like Kingnoor said.
Then slowly build it up until you get a date where you can actually kiss her on the lips.
Then meet her parents, (like Sacrificing said) this will take a load off your shoulders. (Try and give a good impression aswell) (Also don't be nervous once your having a dinner or something with her parents, always try to act confident and be a little bit of a comedian.)
Then after this (if you're of legal age, of course) bring condoms to your date, just in case, and try to make some moves to go to the next stage in your relationship.
If she doesn't stop then you don't stop and you carry on and then you get sex. (Try and do it somewhere comfortable)
After this, you shouldn't be nervous around her.
If you have trouble during these ' phases ' then try and steel yourself in the inside and do it without thinking (nothing stupid though.)
Hope this helps