1. Don't outwardly care if you get her in bed. No pressure on her.
2. Make sure your bedroom, at least, is clean. And that you have sheets on the bed. Fold that huge pile of clean clothes. If your room doesn't look clean and inviting, she doesn't want to be there.
3. Don't ever say, "I'll be the best you've ever had." 100% of the time, she will laugh at you. And you don't need to set yourself up for disappointment like that.
4.Remember: if you're the first she's ever had, you're also the worst she's ever had.
5. If you're both naked and she's laughing, but not putting her clothes back on, that's ok. She's happy.
6. Personalize your speech- Not, "I haven't slept with a woman in so long" but, "I want to sleep with you."
7. If she's doing something to you, try making noises to indicate that you like it. Silence and slurping sounds do not make a sexy environment.
8. Play music in the background, to try and cover up the noises of your housemates and to hide your noises from them. If she wants to be vocal, don't set her up for embarassment later.
9. Tell her she's beautiful/hot/sexy/[your compliment here.] Chances are, she's insecure about her body to begin with and getting naked is always scary. If you can't say something nice with sincerity, you probably shouldn't sleep with her.
10. Take your socks off.