Whats the subject of your blog going to be? If there's words with high competition try being as specific as possible.
you can also check spyfu.com , keywordspy.com, ispionage, wordstream - there are plenty of such services. also semrush, but it has a bit outdated data. wordtracker is good, for sure. also there are few databases on market with such keywords, but i suppose it's not your case to purchase it, because you need only a few kws for your blog. the main idea is to look for what your competitors do. find few small niche sites and analyze them.
You can get help of this local search engines website like Google,Yahoo, Facebook...etc. Because mostly this website use local search keywords. I think what do you want to make a website here you got it.