Acting like you don't care works, but not if you want a long-standing relationship (I'm talking years). If that's the case, being yourself works, unless you're a spaz around girls.

Since you're twelve... not much sex should come from a relationship... unless you live anywhere near california or arizona.

If you have charisma, use it. Even if you make a social fopaw, your charisma can save you if say something convincing.