Top searched words/phrases on Google: Facebook Twitter Justin Bieber YouTube videos Gamezer Katy Perry Netflix Kesha Ipad Chatroulette Nicki Minaj Friv Myxer Shakira Eminem Grooveshark Transformers 3 Miami heat Espn 3 Cricket live score Iphone 4 Cupcakes Jimmy johns Blackberry apps Earthquake Randy moss Haiti Chile Mobile technology Redcross canada Oil spill Rachel ray David villa Olympics Mundial 2010 Fifa 11 Applebees menu World cup Hucg diet Dr oz Csl plasma Kew gardens Oxford street Selena gomez Megan fox Robert pattinson Miley cyrus Kim kardashian Aspergers Master chef Read more: http://writinghood.com/writing/worl...google-tips-for-online-writers/#ixzz1QjbQDLMc
Why not try to check out sites that are sold on flippa. you may check their data and get their targeted keywords to analyze and enter possible keywords which are profitable. hope it helps.
I made myself the same question some time ago, but I think the most important is the most converting words, no the most popular, but all depends on what you are looking for. If you look for sex, celebrities, ufos, politics, fun jokes, sports are some of the most popular themes, however they are not very good (with exception of the first one, but is banned constantly). I hope it helps
Use adwords,its not only free but also gives you detailed information once you login using your g-mail