Although all these rules may seem a little ovibous, it's suprising how often boys forget...
1) DON'T BE CONTROLLING
You started going out with this girl because you liked who she was- not who you're forcing her to be. Let her make decisions. Ask her opinion. Listen when she says no. Give her space and time. Everybody deserves freedom.
2) BE NICE
Basically, the Golden Rule. Don't be hurtful.
3) BE HONEST
If you want to break up, tell her. If you're already dating someone, tell her. Tell her how you feel. Don't lie about things- even small things. Trust is a precious thing.
Yeah, we all know that girls love to talk. So you think boys would have evolved some better listening skills by now. But evidentily, eveloution is a little slow.
Look at her. Ask questions. Pay attention. Respond. It lets her know that she means something to you, and boosts her self-confidence. Anyway, communication is VERY important in any relationship.
5) KEEP UP YOUR END
It really isn't hard. Return phone calls. Make dates. Show you care. After all- a relationship involves two people.
And that's it, really. Be a good friend to your girl- she'll love you for it.