My Experience / Credentials = professional Search Engine Optimizer and WordPress website designer..
Here is an example of how to use a Tag correctly:
Below is a link to a post I wrote and SEO’d for a client’s WordPress website. The primary SEO targets are vehicle graphics and vehicle wraps and this is Regional SEO because the company is not National, they are a based on the East coast in Virginia. So some logical WordPress Tags that work for this particular post are: vehicle graphics virginia, vehicle wraps virginia, etc. If you set your WordPress SEO plugin to index Tag pages then every Tag you add to a post will potentially generate a “new” page. What usually happens is the strongest Tag page wins out over the rest of them for ranking. Or in other words one of your Tag pages will outrank all of the rest of them. You may see several Tag pages indexed for a short while, but the search engine will eventually eliminate the others as duplicate content pages.

You should add no more than 8 WordPress Tags to a post. It is recommended that you keep them relatively short with no more than max 4 keywords.

This is a link to that actual client’s page so you can take a look at the focus of the post and more importantly look at the bottom of the post at the WordPress Tag names.

http://www.visionsign.net/vision/…

Now if you create WordPress Tags that are not relevant to the content of your post then you at best just wasted them and at worst your post will get a very low search ranking. If you don’t care about ranking high on the search engines than you can just fool around with them to piss people off or not use them at all. From a website visitors standpoint they can be helpful to someone if they see the exact WordPress Tag phrase they are interested in. WordPress Tags are just basic keyword links so when someone clicks on that WordPress Tag link it will take them to a post that is hopefully relevant to the WordPress Tag name. That is why WordPress Tags were originally thought up, but like I said they are also a very important part of getting high search engine rankings if you care about ranking well in the search engines.

And one more example of a post I have written that contains a wasted WordPress Tag because I’m really not concerned or trying to achieve any high search engine rankings for this post. The post has clients Google rankings listed on it. I’m only using 1 WordPress Tag on this post >>> Clients Google Rankings >>> you can see what I’m talking about here >>> http://www.ait-pro.com/clients-google-rankings/… Look at the bottom of the post you will only see the one WordPress Tag and like I said this is a completely wasted Tag.

Hope this info helped. Good Luck!