There are some pretty nice tools to help you work out good keywords. I have the pro version but you can try it out for free if you want.
The free version doesn’t have all the articles and there are some other limits but there’s enough there to give you a pretty good idea. Here is a link for the free version [ link redacted, please do not post links in the reviews section ]
I really like all the articles with ideas about how to make money off your site. Not sure if they’re all available in the free version or not but I think that the sub is worth it just for those.