Be supportive of him. Nothing better than a girl who is always in a mans corner. Guys aren't as tough as they appear on the inside. They have fragile ego's as well, and need support. They want their woman to stand by them, and be helpful.
Avoid drama. Some drama can't always be helped. It's okay to talk to your guy over problems that happen. When I mean avoid drama, don't flip out on him all the time. Do not make him feel drained out constantly.
Give him trust. Trust is key in any relationship. If you're not giving a guy, or any person trust, you are pushing their trust in you away. Don't always question his motives and assume the worse. That hurts a persons self-esteem and makes them feel bad. Which in return makes it difficult to keep him.
Don't be so needy. Don't always focus on your needs, and what the guy needs to do for you. It's a pretty big turnoff and grows old on a man. If you don't feel he's giving enough, then that's a decision or topic you are allowed to talk about with him. Relationship is a 50/50 partnership. You can't demand so much out of your partner, where you've become unreasonable.
Don't control your guy. Anytime I'm out somewhere. I see someone's wife, or even girlfriend talking down to her guy. Ordering him around and basically showing she's the dominant person in the relationship. I think to myself, he's got to be the most unlucky guy on the plant. I'm not saying guys should treat girls that way too. Of course it's bad on both sides. Even if the guy is putting up with it, trust me, he's not happy. Don't treat your man like he's five years old in public, or overall. You'll chase him away and eventually he'll have enough of it and move on.
Do things that interest him. Don't always do what you like. Do what he likes. If he likes sports, go to a ball game with him. You don't have to do what he likes 24/7, but I think it's fair to at least try and do things that he enjoys. That's a better way to bond more and become even closer to your guy.