French kisses are kisses in which you also use your tongues. (That's why you part your lips slightly.) So, after you've started kissing, the next step is that either he will slip his tongue into your mouth or you'll slip yours into his. Don't let your tongue go limp but move it around his, or playfully push his tongue out with yours, then let him push your tongue back into your mouth, and so on.

Repeat this until you get tired of it (which you never will!) or until your annoying little brother starts taping you with the camcorder and threatening to tell your parents.