What's your favourite gear ratio?

Hi guys. I'm running as it came out the box; 42:16. As a real novice, perhaps I can ask your advice? I want more speed on the flats. I don't mind making it a little harder on the inclines which I suppose I have to have if I want the extra speed. Is my first step to reduce the 16 or increase the 42?

As I said in the other thread.. stick with it for a while.