1. WordtrackerWordtracker is probably the best tool for keyword research, but it does have a price tag associated with it. However, you can sign up for a free trial and give it a test drive. If you're serious about search engine optimization, then you should use Wordtracker for your keyword research.
The key to using Google AdWords Traffic Estimator for keyword research is to find the middle ground. Look for keywords related to your blog's content that are neither the most trafficked and highest priced nor the least trafficked and lowest priced. This way, you'll strike a balance between too much competition (meaning many other sites are already creating content related to those keywords) and too little traffic (meaning no one is searching for those keywords).