Make female friends (if you're heterosexual). Ones that you don't have to or want to bang and still enjoy as human beings. This can be hard if you're a virgin or haven't had good sex and know what you're looking for in a woman, but one day you'll realize that you don't want to bang just anyone who looks mildly attractive if you aren't past that phase yet.

This will show you that women are normal and make approaching women you're attracted to less intimidating (but you'll always be nervious about that sort of thing no matter what).

If a girl does not want to be your friend (or more but that would be implied from not wanting to be friends), stop talking to her. It's over. Oh well. Shit happens.

Get hobbies and friends to support you who aren't the person you're interested in so that you can find ways to get space when you need it because eventually you will need or want space. Or they will. This doesn't mean forever, this just means on occassion.

Understand that it's a process. I used to be clingy as fuck, but have made great strides in not being so. This isn't to say I'm perfect or anything, but it's something you have to work on and doesn't magically happen over night. Make sure that if you are looking for someone to be with that you don't get hung up on one person either, and talk to multiple women all the time until you've found someone who actually feels the same way back. You can't change peoples minds if they don't like you, so just move on.

Then once you are with them, don't bombard them at all hours of the day. Let them supply some conversation too once in a while, and be their own human being.

If you're gay, well good luck. The pool's a lot smaller.