How to Make a Girl Happy

Become a good listener.
Ask questions about the things she says. Show that you're listening actively, not passively.
Avoid interrupting her. (Of course, sometimes what you have to say can't wait. If this happens, just make sure to return to the subject she was on.)
Don't answer non-essential calls while talking to her. Similarly, if she's talking on the phone with you, avoid switching lines.
If she has just told you a deep personal secret, don't switch topics. She has just confided in you and probably wants you to confide in her.
2.2
Share things that define you. Self-disclosure is essential to bonding and has been shown to promote happy relationships.
Talk with her about your hopes, dreams and fears. Make sure the depth of these discussions is appropriate for the level of your relationship.
Talk about your favorite songs, movies, books, and memories. These seemingly little things play a big role in forming an emotional connection.
Be sure to both listen and share; self-disclosure is a two-way street.
3.3
Be worthy of her trust. There's a reason we say that trust is "earned."
Do not show romantic interest in her friends. Not even a single one of them.
Always tell the truth, even if it hurts. Getting caught in a lie is much, much worse than fessing up to something unpleasant.
Be as good as your word. This doesn't just mean keeping a big promise every now and then; it means doing the dishes or picking up those socks like you said you would.
4.4
Make your enthusiasm contagious. Everyone loves to be around a positive person.
Show that you're genuinely glad to see her. If your usual first reaction isn't a smile, there may be something wrong with the relationship.
If you're just having a bad day, put it aside and grin.
Laugh at her jokes; everyone likes to think that they're funny. (If they're not funny and you're not good at faking, just smile; a fake laugh is much worse than no laugh at all.)
Make an extra effort to cheer her up when she's down. If she's going through something, talk her through it. If she just has a case of the doldrums, get her out of her rut with something fun and spontaneous.
5.5
Don't pressure her romantically. There's nothing sexy about reluctant sex.
If she seems hesitant, back off - even if she doesn't say anything. She may need more time to feel comfortable.
Don't put out the wrong vibes. If she senses that you're impatient, she may grow distant -- or worse yet, do something she regrets.
Remember that no means no. Even if you've been together for years, it's her body and she's under no obligation to share it with you.
If she's an abuse survivor or something along those lines, that's a different situation entirely. Get her to talk to someone if she's not already.
6.6
Know when to give her space. Women are just as turned off by neediness as men.
Have a life of your own. A confident, independent person will never lack admirers.
Don't force-feed a budding relationship with too much affection. This is unhealthy and will raise red flags.
7.7
Learn how to fight. Knowing how to keep your head in a fight will make it productive instead of destructive. And as much as you may want to avoid confrontation, it's far healthier to fight than to sweep things under the mat.
Don't just change the subject when a fight is brewing. Forcing the conversation elsewhere will just create resentment.
If she's really mad, give her a cooling period, then offer to work it out. Never forget to come back to the argument later or you will come off as evasive and/or uninterested.
Admit when you're wrong. Without humility, you will never learn from your mistakes.
Don't use an apology as a tool for ending an argument. This is manipulative and unproductive.
If you really messed up, you might want to plan a special date to apologize.