segment your searches at adwords keyword tool and merge it with google search to get more accurate kws.
Obviously Google's keyword tool is the Best tool online. The basic reason is that no tool can gather information about Global online searches as Google can because majority of searches are been done on Google. Google Adwords is an advertising program run by Google! Many can guess what you were talking about but technically this answer is wrong ..it is Google Adwords Keyword Tool! Then try with Google Trends and Google Insights search tools. They will get expand your keyword research ideas! "It is asking me to Sign in with a Gmail account when I followed your suggestion what should I do?" ~Would you like someone to ask you like this? Why don't you give more?
simply googling a main phrase and looking at the competition is a good starter. You can get tons of info from looking at their page titles, etc.