Get a site and then keep on promoting it through forum/blog commenting, article submission and aother ways.
Check out social bookmarking and social networking sites, those are the easiest way to promote your site. AdSense practically sells itself once you get enough traffic
Right You Dont have to Promote Adsense Ads. First of all Just take some time & Read all Adsense TOS so that you will come to know that what is right & what is not so that you will not get any risk from your side. Then Create a Good Site on that topic you have good understanding then start promoting your site Dont forgot to place Adsense on most visible Places.