Most Helpful Guy
Maybe your just trying on the wrong kinda girl for you. Try befriending the girl first and don't come on to strong right away, most girls hate that. Being funny is not something everyone can do naturally, but what I've recommended to a lot of my friends is not to use pre-written jokes, but use your surroundings and subjects around you and use common sense comments about those things for expample: Kids playing in the tubey slide things at mac donalds, you say "Wouldn't it be funny if one of those kids starts running back to their parents screaming that their brother got stuck again in the tube?" it might sound harsh but at the right moment, it will make her laugh and laughter will make her at ease with you and give the impression that your a fun guy. Talk to her and get to know her likes and dislikes and just listen, don't hear her but listen to her, there is a difference.
Befriending a girl can take up from 1 - 3 months, it seems long but it is what I call "safe time" that they will start to trust and like you more, before you can actually begin flirting.
If you do flirt, don't become a jerk and jealous if she talks to someone else, be cool and introduce yourself with a smile. Yeah that also very important to always keep smiling like a beauty pageant girl, well not that extreme, but you see were I'm getting at.
These are just some pointers I used when I was your age and still in the game.
1 be funny
2 be natural
3 be patient