Dont drink. Be well rested. Dont jerk off for a few days. And relax. Stress is your enemy, cuz she's new, you want to make a good impression. Probably intentionally hold off for a while, to impress her with your staying power, however some guys (myself included) once they hold off long enough, can go on forever - you've missed that golden moment. If that happens, stop / slow down, Let thiings cool off a bit - not completely. go back to kissing, oral, petting and rebuild. The worst you can do is just keep pumping away - you will just get more stressed, and it will be less likely, to happen, and she will get sore and pissed off. Whatever you do - make sure she knows that you are super turned on. Let her know your continuous hardon is evidence of that. Tell her that just like some guys have trouble getting it up when the pressure is on, you have a different situation, sometimes its hard to cum, if the tension / expectation level is too high.
GOod luck