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I would love to know how some of these Adsense experts make thousands from their sites every day. Just HOW do they do it?
1. Pick a niche that you enjoy and can create unique content for.
2. Do what you can to get the site name out to the public.
The important thing is to create a site you enjoy...if you enjoy it, others will. The niche doesn't matter, if you pull in enough traffic you can make money off of anything.
Your problem is not finding a FREE Niche Finder. That is not necessary. You need to research the adsense forum to find out the CHARACTERISTICS of a well paying niche.
Recommendation SEO tools is promotion and we can't allow that here. And since that tool is essentially useless anyway, it's best for you to learn what makes a good niche. You'll do better.
Good luck. ;)