There's no faster way to make your hair dull and lifeless than to use products containing alcohol. Talk about drying. (You'd think they'd leave the alcohol out of hair products, then, but they don't -- mousse is a particularly common offender. Gel, too.)
Look for products that are alcohol-free, especially if your hair is naturally dry. Your hair will be shinier and sleeker for it, and easier to style.
And now, for some ingredients you do want …