For terminology, I will use the following words:

• term – a word or short phrase (also called a tag but this leads to confusion)
• tagging, to tag – marking an article with a term

Each term has a unique page (term page) on your site (e.g. blog/term/world-cup-2011). Articles are usually presented in date of post order with the most recent article listed at the top of the page.

Each term must, as a rule of thumb, be an important keyword for your site. Examples of exceptions to this are 'pdf document' or 'video', you'll probably find a few others depending on your content. If there is an important site keyword but no corresponding term, you’ve missed something. There should (probably) be a term and some articles to tag with it. If not, fill the term gap with a few articles about it. Don’t stretch the content to fill the missing gap.

The term page provides ‘teasers’ of all articles tagged with that term. (A teaser is a short introduction to the article and in our case will be the first paragraph of the full article content).

As a consequence, you should create a 160 or less character description of each term. We put this description at the top of the page as well as in the meta-description that is shown in SERPs

When the full article is viewed (by clicking the link below each teaser), a list of all the terms by which the article is tagged appears below it. Clicking on one of the terms takes you to the corresponding term page.

As you can now imagine, tagging allows people to navigate through content on your site in their own way rather than using the limiting navigation of a menu.

On each term page and each article page we also provide a ‘tag cloud’. This is an area, generally in a side panel, that lists perhaps 10-20 terms. The more articles that are tagged with the same term, the larger the font for that term in the tag cloud. You end up with a bunch of terms in varying font sizes each linking to their own term page.

There is very little point in having only one article tagged with the same term. If you think about it logically, a term that is only tagged once leads the user to a dead end. They open the article, they follow the term to the term page, it lists only the article they have just viewed; they’re in a dead end. This obviously isn’t good as they cannot navigate out and continue browsing related content on the site. The only time you want to do this is when you know that you’re going to use the same term again in the near future. For example, you post your first blog about the world cup 2011. You know you’re going to blog about this every week for a few months so a new term is warranted as the term page will fill up with more articles every passing week.

As far as tagging an article goes, you want to allow for a variety of routes out of the page to other content. Only one term for an article means there's only one way out. On the other hand, 10 terms is almost certainly too much. This isn’t because there’s too much choice but more because you want to present different related content as they navigate through the terms. You can imagine that tagging each article with 10 terms means that each term page has perhaps 20, 30, 40+ articles. After a short time browsing terms, the user is likely to have already been presented with the listed articles (because each article is listed in so many terms). This is a dead-end again and the user will get annoyed navigating to the same content again and again when browsing different terms. Furthermore, we only show 10 articles on a page, the rest are viewable via the ‘next page’ link at the bottom of the page.

Clearly some terms *will* have lots of articles tagged with it and these will be the major subject areas. The smaller subject areas and their corresponding terms will have fewer articles tagged with them.

No term should have all or the majority of articles tagged with it - you're essentially just showing the latest articles and this page is your blog's home page - you're duplicating the content.

You don’t want to tag a bunch of articles with exactly the same terms either as the user will end up navigating around in circles of terms with the same articles just like over-tagging described above.

So:

• Limit each article to perhaps 3-5 terms (this is not a hard and fast rule)
• Try to ensure that each article has a unique combination of terms
• Try to ensure that each term is used 3+ times
• Try to limit term tagging to a maximum of 20% of the number of articles

Happy blogging!