If you want to develop a good personal style, start keeping a scrapbook of pictures and styles that you like, on a daily/weekly basis. Write about what you wear each day, and maybe take a picture to accompany it. Then see what works for you and what doesn't. Over time, this in conjunction with the scrapbook, will give you an awesome sense of style, better than most of your peers.
With makeup, less is more. The more you can look like you're not wearing any makeup, the better.
With hair, try a bunch of diffrent products, see what works, and then switch every so often.