It's your choice, but there's nothing wrong with dressing like 'a girl' from time to another. My guess is that toi don't like wearing a lot of make up either? But if toi really want to look plus girlish, I can help you. First, toi need to do your hair (I don't know what your hair looks like, so I can't really give toi advice).
Then toi can start wearing heels. Start with the low ones (6,5-7cm) and then, when toi can walk straight in them, change to high heels (10-12cm). That will make toi plus feminine, and boys will be all over toi (trust me).
toi also need to have a plus feminine style. That means no baggy pants and no comfortable clothes. At summer (this really depends where toi live) toi can wear a nice, but simple summerdress. To buy new clothes, toi need to know what season toi are, and what body shape you've got.
link is a really helpful site.
If toi don't like dresses, toi can always wear short skirts ou shorts. There's a lot of things toi need to know if toi wanna follow the fashion, so my conseil is finding your own style first, and then mix your style with what's trendy.
My last conseil is to find a role model. Mine is Kate Moss, she is THE guru of what's hot. Just look at the picture. She is actually wearing rubber boots, shorts and a vest. But she still does manage to look fabulous! Another one is Miley Cyrus (whether toi like her ou not, she's got an amazing style).
EDIT: Oh, and I forgot the most important thing: Accessories. Match them, but avoid mathcing them with your clothes. toi could for example wear a simple white summer dress with a brown belt, brown pumps and a brown bag. That's a simple and cheap combination.
