If you guys are on date #3, and she actually likes you, not much to do other than physical part. Kissing, if you guys have good chemistry, will deepen the affection for both of you. Then if it goes to sex and its good that wont hurt you two liking each other more. I mean other than than unless you can present yourself in a way she hasnt seen you through two dates such as learning you have shared interests she cares about, the first paragraph above is the next step. Good luck guardian!