Using the good ol' free Google Keyword Planner is great. But there is an alternate universe of Long Tail keyword phrases that live in Google's other database--namely, their "Autocomplete database." That's the database that is accessed when you're typing queries into the Google search box (notice that list of suggested keywords that pop up as you type?)
Can't go wrong with the Google Keyword tool, SEMRush and Google Trends. The Keyword tool for volume estimates, SEMRush to see what keywords competitors are ranking for/targeting, and Google Trends to make sure the traffic is actually coming from countries I'm trying to target. Gives a relatively accurate picture of when to expect traffic spikes and seasonality insight.

To be able to rank in the search engines is an art that must be understood and finding the right Keyword tool that fits into your comfort zone is a must. What I mean by ‘comfort zone’ is having a keyword tool that doesn’t confuse you before you begin even searching. Some go into far too much detail than is necessary. All you need really are good long tail ‘common sense’ keywords that other marketers may have missed.
1. Create a New Project. By clicking on the “+” icon located at the left upper corner, a new pane will show up allowing you to: enter your new project Title; choose your project’s Country (which affects the total of local monthly searches and top 10 Google results shown); pick your project’s Language (which affects generated keywords and the top 10 Google results for users that use that language); select your Search Network (which affects the number of reported searches depending on your choice between “Google” or “Google & search partners”); and toggle the Adult Ideas switch on or off.

Most people who use the Google’s auto complete feature to generate keywords that they include in their blog title or page find Soovle to be a very useful tool. This tool moves the auto complete feature a step forward by getting inputs from several sources like Amazon, Yahoo, Wikipedia, Bing apart from Google itself. This assists the user to generate keywords that drive online traffic in a better way. The default is usually set to Google but you can switch to the other options at your own will and view how the outcome keeps on changing. You can experiment with a broad range of keywords by running them through a specialized tool such as the keyword inspector as a way of extracting value that will boost your sales on Amazon.
For the first few months, there was certainly a transition period.  However, the new team was able to take over the reigns fairly quickly.  A big reason for the quick transition is because I had automated most of the business already.  So, the fact that I was stepping away didn't make a huge difference since all the sales, marketing emails, and many other details were already happening on an automated basis.
In a nutshell, Long Tail Pro helps you quickly find keywords in bulk based on a seed keyword that you input.  In addition to returning hundreds of related keywords, the tool also shows search volume (monthly search volume), advertiser bid, number of words, rank value, and my favorite Keyword Competitiveness (helps you judge the competition and keyword difficulty).