Even with such amazing tool as “keywords research” from G adwords you still have to turn your logic on to filter out keywords which couldnt possibly be good. Sometimes its too hard and you fall into traps like I did myself  couple years ago when I ranked in top 5 for “casino gambling” and “online casino gambling” which were highly recommended and competitive keywords from G adwords (and still are) but I saw only couple of visitors from those keywords each month.

That pushed me to creation of tool to help avoid this issue in the future (sry, not for sale). All I can suggest is to avoid looking “fishy” keywords and trust your instincts.