If you're not busy, I highly suggest you read all of this post: The Benjamin Franklin Effect

If not, I'll give a quick TL;DR. Benjamin Franklin once competed with a man for office, and tensions ran high. Franklin wanted to make a friend of the guy, so he sent a letter requesting a book from him. This act led to them becoming friends.

Why did this happen? Because most people have horrible misconceptions of how people build opinions of each other.

Most people think that "you do nice things for the people you like and bad things to the people you hate." Well, in reality the opposite is true: "you grow to like people for whom you do nice things and hate people you harm."

Why does this happen? Because our brains don't like dissonance. We like to form a solid image of our own persona that is consistent. Often, our actions are not reasonable (starting to sound familiar? hamstering!) and we rationalize our character (malleable) to match our actions (unchangeable).

So, now that we've established this, how can we use it? Do what Benjamin Franklin did: ask favors of people.

Instead of taking a woman out on a nice dinner (typical nice guy behavior), try asking her to bake cookies for you. If you convince her to bake you cookies, she will rationalize that she must like you, because why else would she be baking you cookies? Simple, succinct, and effective.