I've got the big iPad and have the apple Smart Cover (or whatever they call it) and that's great for keeping everything clean etc (and when you close the cover the screen shuts off/goes on when opened).
Or if you really want to protect it then go for something like the otterbox defender series, I'm getting one for mine and after having them on all my iPhones they seem to be getting better and better (the 3G had few scratches on after two years, the 4 looked like new and just installed it on the 5 and the case seems to have even better protection)
It all really depends on your budget to be honest.