i just format it once, or if i am feeling lazy i just ask if they mind me seding them an unformatted drive. most of the time people like getting whatever is on my drive, mp3s, or whatever else might be there
most of the time i just formatt it once and send it on its merry way
well if you really wanna be sure, a program like gwscan canbe used to competely erase the drives (google 'gwscan') and that completely gets rid of anything that could ever be pulled off of it. other than that, they say 3 full normal formats will do the same thing, but i think its takes longer