Nope, never click your own ads, in theory there is a test area inside your google adsense control panel. But, no, never click your own ads. If you can see them, they are working. (Unless you're messing with the code which you shouldn't be)
No, one click maybe acceptable, as it can occasionally happen by accident, but click on four or five = ban. email a friend and get them to click on one to test it if you are that worried. (I do not condone clicks for the sake of clicks but I can sympathize with your worry)