I know you shouldn't spend 5 months building your product before releasing it (been there).
I know you shouldn't rely your own assessment to think your idea is great (been there too).
I spend some time trying to validate my ideas before trying to launch something (and have a nice graveyard of ideas that passed away).
I usually rely on Google searches, Google trends, Google Keyword Planner, namemesh.com, ranktank.org and track everything in a spreadsheet.
Which tools do you use to track and assess your startup ideas ?
