So whilst Long Tail Pro has just continued to grow in revenue every single year and comes highly recommended, you may want to check if all the important features are fully functioning before signing up. Especially the KC feature (keyword competitiveness) as it is so fundamental to keyword research and making an informed choice on whether or not to go into a particular niche.
Although more and more keywords are getting encrypted by Google every day, another smart way to come up with keyword ideas is to figure out which keywords your website is already getting found for. To do this, you'll need website analytics software like Google Analytics or HubSpot's Sources tool. Drill down into your website's traffic sources, and sift through you organic search traffic bucket to identify the keywords people are using to arrive at your site.
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).