You can use Keyword Researcher Pro with the best free keyword research tool out there, Google KW planner. Importing and exporting data is as easy as clicking a button. It’s all done at lightening speed too. There are tutorials of how to do this in video form on the sales page here and they show just how easy this tool is for finding those long tail keywords.
Use the Google Adwords Keyword Planner to find new and related keywords, but ignore the search volume data! The search volume data in the planner is really only useful for keywords that you’re actually spending money to advertise on. Otherwise, these volumes are not reliable. While not really helpful to decide which keyword is most used by your potential audience, Google Adwords Keyword Planner makes a useful tool in coming up with ideas for potential keywords!
But maybe you didn’t watch the tutorial video yet. Or maybe you didn’t know about the extremely powerful KC feature. Maybe you didn’t know how quickly, easily and effectively you could analyze Google top 10 search results with Long Tail Pro. And maybe you didn’t even know how profitable it can be to simply target just the really long tail keywords.
Given you have a good idea of where to start and are fairly confident you are speaking the same language as your client, jump start research by generating related keyphrases and long tail variants with the ever so easy to use Google Autocomplete. This tool makes predictions based on what you are typing that are a reflection of Google search activity.
Finding the best keyword research tool also depends on your own experience with SEO subjects such as buying keywords, long tail content, long tail SEO and using low competition keywords. For instance, a newbie looking to use long tail marketing may find something like Long Tail Pro V3 a little too confusing and a bit expensive as it’s a monthly fee and has a confusing interface.
I just have the free version right now so I don't know all that the pro one can do. But even the free version has A LOT of tools you can use, I haven't even figured them all out yet. But one that I have used is their Content Optimizer. You can take a new or existing content piece of yours, and compare it to one of your competitor's pieces on a similar topic, and see where you might be lacking based on the keywords that are used in each piece.
Long Tail Pro is a keyword research tool that helps you quickly find low competition keywords for your website. In particular, the tool is built for people doing SEO (search engine optimization) as opposed to people doing paid ads (Google Adwords PPC). I'm sure there are some advertisers that use the tool for paid ad keyword research, but the tool was built for SEO keyword research.