depo provera is a shot taken every 3 months, either in the ass cheek, or the arm. it's not bad at all. possible side affects could be weight gain, depression, the same really with anything. it is hormones. this is my method of choice, and i don't have any problems with that.
the patch is newer, it is exactly that, a patch. it is placed on like the ass, the backside, the arm, i think. i think it is replaced every month. it's like a sticker. my girl uses this, cause she didn't like depo. made her gain weight.
then there are iud's or something, where they place this little metal thing in your skin, wouldn't recommend it, but hey!
my favorite are these little vaginal films that she places in her vagina lbefore sex. it dissolves, and is like 96% affective ALONE. so if she acts stupid about the previously mentioned devices, go get some of these, and make her ass use them.
go to planned parenthoods website, they can give you more info, and clear up anything i may have left out.