Drink plenty of water, eat a healthy diet, keep your face clean and moisturised and try not to touch your face too much; dirty hands = blocked pores
This is excellent advice, it drives me crazy when friends of mine complain about their skin and then spend half their time pawing it and touching their face. Your hands are the alpha breeding ground for bacteria on your body, keep them away from your face.
Frankly vitamins and sun are both pointless at best and counter productive at worst.
The best thing to do if you're really worried about your skin is do what Nudey told you to do, get plenty of sleep and a decent Dermatologist, keep your skin clean and exfoliated and find a skincare range which is designed for your skin.
This last piece of advice is tricky because (as I know all too well) it can be costly, but if you want movie star skin you'll probably have to pay movie star prices for it.
A good regime of facials can help but don't get them too often.
The whole "eat raw veg all the time and cut animal fats out of your diet completely" thing is bullshit. You need a balanced diet with plenty of veg and a normal amount of animal fats, especially since the body needs a variety of different fats in order to function properly, and as well as olive oil and other vegetable fats you do need some animal fats too, especially fish fats.
Your skin often reflects your overall state of health, so punishing your body with alcohol, drugs, late nights and bad diet will show big time. My dermatologist can tell when I've been over doing it with boozy nights out instantly and recommends I use tincture of Milkthistle to help improve my liver function to help my body repair itself and expel all the toxins and stuff.
If you smoke then either quit or like me be ready to spend foooooortunes!!! on repairing the damage by putting back all the stuff smoking destroys with expensive products.
Someone already mentioned exercise in this thread, that doesn't look like it'd be a problem for you but getting lot of it is great for your skin, as is lots of sex.