When it comes to frustrating hair moments, nothing hits quite as hard as when you've taken the time to style your hair straight only for waves to slowly set. (The same can be said for defined curls that wind up surrounded by a frizzy halo.) Like most hair conundrums, there are multiple causes behind your hair not cooperating. But the first step to solving hair that won't stay smooth happens in the shower. To give your hair a fighting chance against static and frizz, you need to start by using one of the best shampoos for frizzy hair.