Well, since most of my friends are girls, approaching them is not a big deal to me. Just treat them like you want to be friends with them. Try saying "Hi" to them. Just remember to be yourself--if they don't like you the way you are, it's really pointless to go for them. You want someone who will accept you as you are, not some fake personality you make up.
The number 1 mistake is trying to get every girl to like you. It DOES NOT work. Lying to them about yourself will make things terrible, and they will hate you. Trust me, you want a girl who will accept you the way you are, so be yourself.
Hope this helps.