Follow these steps to a cool room that every girl will envy!

[edit] Steps

Put your bed to the side of the room.Put it up against the wall.
Get a giant mirror and put it where you can see your whole body.
Find a clothing rack and put on brand or style of clothes on it.
Keep using clothing racks or hangers for your clothes
Make a stage. If you want to go completely wild, make a Red Carpet or a Fashion Model Stage that you can walk on. Add chairs at the end so your friends can rate your outfits.
Have a stereo that plays the "in" music for your age. It gives a feel that you are really shopping.
Collect shopping bags from places where you like to shop and when you pick out an outfit, use the bags!
Have a whole shoe department. Spread a large colorful rug on the floor and put your shoes on it, on the wall beside the rug, and/or a shoe hanger.
Find old shoe boxes and tissue paper to create an even better shoe store look.

[edit] Tips

Make sure to leave room for sleeping! a canopy bed with shoe or purse fabric might be a good idea, so that you're bed isn't messing with the scene.
Everyone loves mannequins. Whether you have space for them or not is another thing. You will, of course, also need a feather duster to keep them pristine.