I know it sounds crazy but How do break my arm?!

Stretch out the chosen arm and jump with all your weight on to something like the sofa or the floor, watch you don't bump your head.

Best way to do it.

umm... well you could fall out of a tree or you can have a friend push you on the ground. thats how my cousin broke both his arms! :(

my brain duhh. why do they even ask this question

Put your hand on a table leaving your arm in the air and hit it

Start hammering your arm. I hope you don't do this though

umm......i think thats a bad idea!!!