My question was what is the right way to use them. Are words like: is, are, and, of, in, a, an, etc. considered to be vital or should I omit them?
The right way to use them is as content, completely written, marked up semantically. They have ZERO business in your keywords META because that is not what said meta is FOR.
Though if single words in them are important, put a
copy of those words with unique meaning in the META. Just remember to limit yourself to just eight words from the entire page. No more!
No more... What are these words? Explain! EXPLAIN!!!... and that means 8 words with actual meaning unique to the content, so yes adverbs, conjunctions, and the like have no business in the META... but again, long-tail phrases have NOTHING to do with said meta. AT ALL. Zip, zilch, nein, nada.
But when people talk long-tail phrases, they should be talking about content inside <body> and placement in semantically higher ranked tags like your numbered headings or inside <em> or <strong>. As complete phrases or even sentences they should use proper English (or whatever the language in use is) so yes, long-tail should include those words when in the content -- inside body -- aka where they go!
Anyone out there talking about long-tail keywords AS something involving the keywords META isn't qualified to flap their yap on the topic, and is probably trying to pack you full of sand.
Sadly "long tail phrases" if repeated on a page are bad writing, not "writing for the user" and whilst it may provide a short term boost in the rankings, it can also get you pimp-slapped clear off the SERPS for obvious abuse / gaming of the system.
Part of why I think "long tail phrases" are more SEO scam artistry than useful content generation. Type of thing that gives you a brief and temporary boost, but over the long term does more harm than good. PARTICULARLY given how the way many SEO "experts" slop them into pages is actually bad writing.
Again, what Matt Cutts told us all those years ago: "write for the user, not the search engine."
If a phrase doesn't occur naturally during content generation, shoe-horning it in "'cause teh surch enjens" is NOT "writing for the user". It's gaming the system and whilst it might trick the engine in the immediate, don't be surprised if Google's anti-spam division sees it and decides "NO SOUP FOR YOU!"
I've watched that happen a few too many times to people suckered by people who "specialize" in just SEO -- completely banned from the listings from abuse.
Which is a horrifying prospect!It's part of why a lot of these tricks exist and are promoted as they ARE sure-fire ways for a quick up-rank, but only last long enough for "the expert" to
Billy Joe and Bobby Sue their way to the horizon -- or WORSE use the devaluation in a couple months as an excuse to keep milking the client's wallet. Either way not a particularly ethical approach for doing business.