Step 4

Check for a mix of head terms and long-tail keywords in each bucket:
It's important to check that you have a mix of head terms and long-tail terms because it'll give you a keyword strategy that's well balanced with long-term goals and short-term wins. That's because head terms are generally searched more frequently, making them often (not always, but often) much more competitive and harder to rank for than long-tail terms.
Think about it: Without even looking up search volume or difficulty, which of the following terms do you think would be harder to rank for?
-how to write a great blog post
-blogging
If you answered #2, you're absolutely right. But don't get discouraged. While head terms generally boast the most search volume (meaning greater potential to send you traffic), frankly, the traffic you'll get from the term "how to write a great blog post" is usually more desirable.
Why? Because someone who is looking for something that specific is probably a much more qualified searcher for your product or service (presuming you're in the blogging space) than someone looking for something really generic. And because long-tail keywords tend to be more specific, it's usually easier to tell what people who search for those keywords are really looking for. Someone searching for the head term "blogging," on the other hand, could be searching it for a whole host of reasons unrelated to your business.