Getting a sexy tousled look with fine hair is a little more work, but definitely doable. Wash hair with a volumizing shampoo-skimp on the conditioner since you want healthy hair but don't want to weigh it down.
Spray volumizer all over and blow-dry hair fast and furious without a comb or brush, just shaking your fingers through to rough up the texture.
Once it's absolutely dry, use a bit of dry shampoo to ramp up the bedhead-y texture.