they know much more than you can think ... so work and build a serious website and be honest, if you can't then adsense isn't for you
Dont click ads, like someone up there already said, firstly its not worth the effort and the risk of you getting banned is quite high, say about 99% if you do it everyday!
Against TOS. You will get banned. Trust me, a few extra $$ now is not worth losing your adsense account