Chapter 10 Install and System Administration for FortiOS 5.0 : Advanced concepts : Tag management : Tagging guidelines
  
Tagging guidelines
Given the ease that tags can be added to elements in FortiOS, it makes sense to jump right in and begin applying tags to elements and object. However, this type of methodology will lead to problems down the road as new elements are added.
A methodology should be considered and developed before applying tags. This doesn’t mean you need to develop an entire thesaurus or reference guide for all possibilities of tags. However, taking some time to develop a methodology for the keywords you intend to use will benefit later when new security policies, addresses, and so on are added. Some things to consider when developing a tag list:
the hierarchy used for the organization such as region, city location, building location
department names and if short forms or long forms are used
will acronyms be used or terms spelled out.
how granular will the tagging be
As tags are added, previously used tags appear so there is an opportunity to use previously used tags. However, you want to avoid a situation where both accounting and acct are both options. This is also important if there are multiple administrators in different locations to ensure consistency.
At any time, you can change or even remove tags. It is best to do a bit of planning ahead of time to avoid unnecessary work later on.
See Also
Tag management
Adding and removing tags