Other than Google Adwords, how do I find effective keywords?

Many things need to be considered when planning an effective SEO strategy however the most important of all is considered keyword research. I know how it is done, but I am looking forward to find all other ways which can be used to find effective keywords to target for a website.

 

I use freekeywords. wordtracker. com

 

I think google adword is the best tool for keyword searching