Read this interesting article.
It says that if you want someone to like you, make them do YOU a favor!!
Yeah, you read it right. Even if it is as small a favour as lending you their pen or something like it.
It makes sense to me, let me explain how:
When a person does a 'favor' to someone, they consider their action to be benevolent, thus making them feel good about themselves. Of course, since the favoree ( ;) ) is the one associated (although subconsciously) with them feeling good about themselves. The person would end up, subconsciously) liking the favoree!!
Just my way of rationalizing this seemingly irrational behavior.