@clintflint - It does depend on what kind of hair you have though. With fine, straight hair, I wouldn't leave in conditioner, because it will just make it look limp and greasy. You've got to make sure you get the right kinds of products for the type of hair.
I actually find that the best thing I can do for my hair is take regular vitamins. It really helps my fingernails as well. I don't know why it makes so much of a difference, because my diet is fairly good and I would have thought I was getting everything I needed.
I also try to keep it cut to get rid of split ends, since those tend to go frizzy as well if I put off a visit to the hairdresser for too long.