It's your choice, but there's nothing wrong with dressing like 'a girl' from time to another. My guess is that wewe don't like wearing a lot of make up either? But if wewe really want to look zaidi girlish, I can help you. First, wewe need to do your hair (I don't know what your hair looks like, so I can't really give wewe advice).
Then wewe can start wearing heels. Start with the low ones (6,5-7cm) and then, when wewe can walk straight in them, change to high heels (10-12cm). That will make wewe zaidi feminine, and boys will be all over wewe (trust me).
wewe also need to have a zaidi feminine style. That means no baggy pants and no comfortable clothes. At summer (this really depends where wewe live) wewe can wear a nice, but simple summerdress. To buy new clothes, wewe need to know what season wewe are, and what body shape you've got.
link is a really helpful site.
If wewe don't like dresses, wewe can always wear short skirts au shorts. There's a lot of things wewe need to know if wewe wanna follow the fashion, so my advice is finding your own style first, and then mix your style with what's trendy.
My last advice 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 wewe like her au 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. wewe 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.