2) SEMrush- This tool offers fantastic competitive research around domains to find what keywords could be driving traffic for your competitors. Looking at paid keywords ad spend can also help you know which keywords might have monetary value worth pursuing organically. If a competitor is willing to spend a high ad budget on terms and you think they do a good job running their ad campaign, then its a good indication it is worth organic ranking effort.

"With Google giving over the home page to ads and their own properties for commercial keywords, the Long Tail keyword is more important than ever. If you have a website, you know that most of your traffic comes from keywords you never would have thought of. With Keyword Researcher, you can find them in advance and make sure that you're the one that snags this traffic. I use it for all of my e-commerce site planning."

There is no doubt that there are various keyword research instruments out there, however, many people were often disappointed with many of them because they fail to deliver the expected results. While some of the tools proved to be helpful when you look for specific niche keywords, others were simple failure. You would discover that as time goes on that, it begins to slow down. This affects the efficiency and the speed. This is not the case with Long Tail Pro. It does not only deliver efficient and reliable search results, it does it very fast. You would appreciate the efficiency of the tool when you have watched the demonstration videos and tutorials.
Once you've entered a keyword, you'll be presented with a range of data: Google Search Volume, Competition, CPC, and Opportunity Score. This data provides advertisers with at-a-glance data that they can use as the basis for their next campaign. No other free keyword tool provides as much free keyword data as WordStream's new and improved Free Keyword Tool. Try it today and see how much easier keyword research can be with WordStream.
Note: If you can’t justify using Ahrefs on a monthly basis, you could sign up for a month, do your KW research and cancel. That said, if you can justify the monthly pricing it’s well worth keeping because you’ll get access to the ongoing functionality such as rank tracking and web monitoring. It also means there’s no need to use any other tools to track rankings or monitor mentions on the web.
I use Ahrefs to find ideas for keywords to add into content, and content to create around keyword opportunities. I like how Ahrefs shows keyword difficulty, search volume, traffic potential (how much organic search traffic it’s possible to get when you rank #1 for a parent topic keyword) and lets you group keywords together to create lists. It’s really useful.
This is slightly more complicated than it used to be, because you have to actually create a live AdWords Campaign as part of the process! This puts many people off, as it looks as if you have to actually advertise in order to use the tool. You don’t — you can just setup the campaign and then pause it before it runs so you don’t have to spend a penny.
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.