Do some keyword research on the topic by using allinanchor: your keyword and this will give you some idea of your competitors and then check the exact usage of that word in google adwords. This should help you get started.
Adwords keyword tool will give you a better suggestion than any other tool. Also it gives the approximate searches in the past two months.
freekeywords.wordtracker.com www.pagerank.net/keyword-suggestion/ www.keyworddiscovery.com/search.html
You should do your keyword research prior to starting your website. It will help provide a guide for you to follow when you're building backlinks for your site. Otherwise, you'll get frustrated very easily without a gameplan in place and wonder why you don't have any traffic. Hope that helps!