Avs,
firstly for chicks - The big O.
In my experience I have found women to orgasim by one of two ways.
1 - My penetration, by having sex - generally when she is on top.
2 - My stimulation, using your hands or mouth may work.
So in saying this, it's all a matter of finding out which will get her there - also keeping in mind it is difficult to bring a girl to orgasim if she has never had one before, she too must learn about her body.
As far as making the first time special, it's no big deal - take her to dinner, do your normal thing - no expectations, make that clear and make sure you're both comfortable.
As far as you not having been with anyone and her having had sex previously, take that in your stride - be confident!
Good luck.
P.S Don't be affraid to use google to search for tips and hints, there is some relevant ones out there.