The key is traffic, of course, but to get traffic, you need to work hard ! Thats the main advice I can give you ... work hard !
I would say there are no easy ways to make $100 a day, especially using AdSense. You will have to work a lot. Create an unique content site or some online service. Start with something you like, read a lot, learn a lot... be patient, and maybe after 6 months you will make good $$$.
Yeahh i would say to try to get as much targeted traffic as possible. You could even set a goal for 1000 UV/day and then keep going up
That's certainly requires some effort. You may find accurate information all over the net, you even dont have to buy some guru ebooks. Also WSO's maybe usefull. And there are blackhat techniques, too