I've been in my relationship for coming up to 3 months now, and although that's fairly short in comparison, it's the first relationship I've been in since I got into Game last year and I feel like I've learnt so much.
First and foremost, you don't have to be a complete dick to keep her. It's perfectly fine to be nice and compliment her, as long as you're not doing it all the time, making compliments for specific to her help too, rather than just constantly saying "you're beautiful" compliment her clothing, her necklace, etc.. and make sure shes not ruling your life. If she asks you to text her when you're leaving her house, swing it around back onto her and get her to text you. Simply saying "Oh, you text me, its easier" usually does the trick.
Help her with things. Last night I was around her house and she needed to study for an exam she had this morning, instead of just sitting there, I took an active role and helped her revise, she left me a message this morning saying
"I just wanted to say thank you for helping me revise yesterday ^^ I never felt so confident in an exam so hopefully that's a good sign :3 guys don't normally bother helping me or care about my work but you're different

"
So, simply by helping her out occasionally is good too.
I realize that this post sounds rather AFC, but I don't think I am being AFC. I'm still in control in the relationship, if she asks to meet up and I'm busy, I will tell her that I'm busy, instead of dropping everything just to see her. I tease her when I'm with her and laugh at her occasionally. She's said that I'm always challenging her a number of times, simply through making her do things first, asking her to get out of the bed to turn off the light, even though I'm closest to it.
And something that's also very important. BE GOOD IN BED! If you're not good in bed, shes going to be looking elsewhere for a good lay, perhaps not right away, but eventually. She's said that I'm the best I've had, and I believe her because I've also had her friends telling me that shes been saying that. When we're together, we have sex roughly 1-3 times, sometimes all within an hour. She wants sex from me frequently, and the further we go into the relationship, the more we seem to be having sex, usually, it dies down after a while.
We go out occasionally to parties and have a laugh too. So, be fun, be challenging, be loyal, help her out and be good in bed.