Condoms don't work as well as the pill, but if you use a condom you can be pretty damn sure you're not going to get anyone pregnant unless it breaks or unless you don't change it every time you bust a nut.
Never try the pull out method. I used to do that, until my gf got pregnant. As sick as this is, fortunately she had a miscarraige.
I know at least 3 people who have kids now beacuse they thought pulling out before gettin off would keep pregnancy from occurring. I'd say this is probably the way people accidentally get pregnant, but I'm not basing it on stats, just on the people I've met at a young age with children.
Life is a sexually transmitted disease.