Let's start by defining 'long tail keywords'.
A long tail keyword is nothing more than a key search query or phrase that a person types into their search engine to find targeted sites containing just the information they are looking for.
If your site comes up in this search, you have a qualified buyer! Example - let's say you are a whitewater rafting company offering rafting rides in Bryson City, North Carolina.
If you use the keyword 'travel', will you rank in the search engines for it? Not no, but certainly no.
Travel will bring up sites like Travelocity, Expedia, airline sites, hotel sites, travel agency sites - but not your site.
You are competing for a huge keyword.
But what if you use a long tail keyword phrase like 'white water rafting in North Carolina'? Now that's targeted! Will you get as many visitors as you would if you even could rank for 'travel'? No - but the visitors you get will be highly targeted, highly qualified prospects.
Write a blog post entirely about white water rafting in North Carolina.
Use your long tail keyword as your ONLY keyword for that post.
Then find another long tail keyword - maybe 'tubing on the Nantahala' and write a post dedicated to it.
Use that as your only keyword for that post.
The more you do this with long tail keywords for your area of expertise, the more pages you will have ranked in the search engines and the more targeted visitors you will get.