This might be the single biggest one of them all; men want to be desired by women more than they want anything else in the world. For most of them, it's more important than the car they drive and how much money is in their bank account. If they don't believe they're attractive to the opposite sex, their confidence falls through the floor.
A lot of men grow up wanting to be sports players, or music stars, and almost none of them will achieve that dream, so you need to fill the gap for them. Become their biggest fan and their most enthusiastic supporter. Tell them how great they are, make them feel wanted, and always leave them feeling that they can't get enough. Men who feel desired are happy men, and happy men are better to you!