How do you ask a girl to do it?

Even with a condom and birth control pill, correct me if I'm wrong (I'm not a girl, contrary to popular belief, lol...).., but even with both of those applied, isn't there still a 1% chance or something of the like of still being impregnated?

I thought birth control pills stop the implantation of the egg onto the uterine wall, therefore eliminating the chance of conception. :f6:
Someone correct me if I'm wrong.