When coming up with my keyword for my article I always use Google adwords! if im writing about acne ill type in remedies for acne. i find the keywords that have between 1000 and 2000 searches per month. then i go to google and lets say the keyword i found was herbal acne remedies. i just type in "herbal acne remedies" and click search. if the results show 50,000 or less in the search then I know that it will do well in the ranking! hope this helps!