I see a lot of guys saying here that a site must have a lot of traffic to make money from Adsense which is true in a way, but not always...

I have made websites in the past that generated thousands of visitors per day but made very little money and now lot of niche sites where the traffic is pretty low but the CPC is very high.

I think its important to see how competitive a niche is and how can you rank really well before you waste a lot of time putting up websites that don't make enough money or attract enough traffic.

If your website or blog getting good traffic and its gets popular with important topics to them peoples then you can earn money from Adsense. how to do that i hope this link will help to you.
in.answers.yahoo.com/question/index?qid=20090502230933AAo4jfK