I've been very lucky to never have nicked any of my four. I don't put the clippers right to the skin at first, I gradually work my way down. Since I bathe and trim mine everyother weekend, it doesn't grow too fast in that area to have "cling-ons". I not only shave their little buns, but their pee pees too. The more you do it, the better at it you get.
Just don't be nervous and have your hands shaking. That would be scary.
