3) Google: This is pretty straight forward but it’s the main reason I like it. I search for my main seed keyword in Google, and use the keywords that Google itself highlights in bold on the search results, plus the “Searches related to” section at the bottom to get keyword variations or LSI. That’s basically what Google is telling you that topic is about. No need for a thousands other tools. I use these to optimize the on page of my target pages as well.

Scout is an easy to use extension tool for chrome browsers that turns your website into a significant keyword generator. By a click of mouse, you can uncover relevant keywords in your industry by choosing a website that is successful and attractive to your audience. You will be able to understand the true language of your successful audience and generate keyword ideas that you can use in your marketing strategy.
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).