1. Be nice, be courteous. Not just to her, but in general.
2. Be responsible. Get a job, take care of your car, pay your bills. Have your own place. We do not want to take care of you; when we're ready to take care of someone irresponsible, we'll ask you for children.
3. Have some respect. You are not entitled to sex. Even if you've had it with her before. Even if you've had it with her A Hundred times before. As a matter of fact, you are not entitled to anything that doesn't belong to you, and that certainly includes a woman and whatever is hers.
4. Don't be clingy or possessive. If she wanted to be smothered, she'd crawl under a body pillow.
And most importantly: No power struggles: Yes! She is just as smart, witty, charming, sexy or whatever as you are. You should be happy about that--not insecure.
Good luck.