To be honest, you don't have to cover your face with a mass of makeup to look good, quite the opposite really! For me, confidence with yourself helps reflect and illuminate your features.
For the most part, just by keeping your skin nice and radiant, you already look "great". The point of makeup is to just accentuate the beautiful features you already have! Find foundations or concealers that match your skin color, and don't try to be one of those girls who are white as snow yet insist on trying to pull off a dark beige foundation, that is probably one of the most unattractive things you can do with your foundation. If you are going to wear foundation, apply it sparingly and make sure it blends in well, it's deigned to make your skin look as if you aren't wearing any at all.
Another big aspect it your eyes. Although we all have fun seeing bold designs in magazines, billboards, etc, those aren't realistic for every day lifestyles. Use more neutral colors during the day and save your bright blues and greens for special occasions. Actually, all you really need to look "great" is perhaps a little eyeshadow, sparse eyeliner, and mascara!
If you want, use a little blush to give your cheeks a more rosy glow. If you are wearing foundation topped with powder, topped with who else knows, this is a DON'T. Blush over all of this will just show up grainy and won't blend in well. You want to achieve that nice, flushed pink which looks great on just about everyone.
If you follow the few steps of just keeping your skin nice and light, but well-down eye makeup, you're sure to always look alert and well put together!