Hmm, I'd say it's put pressure on the saddle and use it to control the bike. Know that if you swerve your hips a little to the left, it will somewhat "throw" the handlebars in that direction and vice versa, so don't over do it. Big factor, relax, use the trunk of your body to guide the bike.

Sometimes I will use the inner thigh to bring the bike back in the direction I want it to go if it tends to slip away.