You can use google adwords tool for searching the relevant keyword. But instead of using any tool , do it manually. Observe about words which people use most for their search in your field. And as per that create your keyword. So when people enter the word , your site will be shown with similar words. But provide the best and quality information with the keyword.
Google Keyword Research too is one of the best popular and reliable tools for Keyword Research. If you put one keyword in Google Keyword Research tool then it provides you 100 suggestions of synonym keywords and it also show competition Global and local for each. So you can easily make decision which one is best for you. Google Keyword Research Tool - https://adwords.google.com/o/KeywordTool
I agree that google keyword tool is most common one to find the keyword as per the searches, but few more are there like webceo, wordtracker, keyword spy in paid version.
I use Google trends and the Google Keyword Tool. I have always wanted to try Wordtracker - perhaps I will try it this year.
i used to use for free ==> wordtracker and google adwords tools, and for paid tools I love LTP is faster and more accurate result rather than MS