Do talk about:
How amazing you think she is
Her interests
What she wants out of the future
What you want out of the future
Shared experiences or other things you have in common
Do not talk about:
The old stand-bys: money, politics, and religion (unless you know her very, very well)
Other women
Poop jokes (should be obvious, but seriously)
Why your life sucks and how it's never going to get better
Things that you know she finds offensive
Do take the time to pay her a lovely compliment every now and then. Think about something you really like or admire about this girl, and phrase it in the most genuine and flattering way you can. If you can do this right a few times, she'll melt.
Do talk about sex in a dignified way, if it naturally comes up in the conversation. Be subtle about acknowledging your sexual side — you don't want to intimidate her, but you also don't want her to forget that it's there. For example, you could say "Sleep is my second favorite thing to do in bed" or "I might need a cold shower if you keep talking like that."