How can I stop pre-cum from coming out?

It's great when you're masturbating – I love it then. But when I am making out with my girlfriend, I start getting it, and I am afraid she will notice it. It is kind of embarrassing.
- age 16, Missouri

Sorry – that's part of the way the male body works, and there's nothing you can do about it (short of avoiding getting aroused). Perhaps if you tell her about it sometime, though, she won't be surprised if she sees it happening.