The simplest KW research tool is google. Type in your topic and scroll to the bottom to see what related results show up. Use those to either write an article or to supplement other articles with some of the keywords. Yes, they are primary phrases so you may not rank for them right away but building your site with these in it will help get rank for them eventually. Also look at what other articles that show up for the keyword use.
Here is the part of this post that we’ve all been waiting for. How to make Long Tail Pro pay for itself! I can tell you with absolute certainty that all of this isn’t just fluff designed to try to get you to buy the product. I’ve actually done all 4 of these things – and I continue to do the top 3 to this day! This stuff really works and I make WAY more than enough money, as a result of using Long Tail Pro, to pay for itself.
Note: the old software version of Long Tail Pro would have spit out several hundred adwords suggestions (many being irrelevant to the seed keyword) for this one seed keyword and then you would have to filter to see only what you wanted to see. With the new cloud version of Long Tail Pro, you set it to show only a certain number of keywords and it displays the most relevant keywords so you have less noise and confusion to filter through.
2. The second category are keyword tools based on the competition. One of the first things to determine is not only who the business competitors are, but who the SEO competitors are. Keyword research can be done by simply doing research on high-performing competitors. Some of my favorite domain-based keyword tools are SEMrush, SpyFu, and BrightEdge's Data Cube.
Long tail keywords can find people who are later in the buying cycle, and more ready to buy. For example, somebody searching for “tents” is probably early in the buying cycle, just starting to research what they want. Whereas somebody who searches for “North Face Kaiju 4 person tent” already knows what they want, and is more likely to be ready to buy.