The big basis of tagging is the sole principle of tag what you see.
If it's a cub image, tag it. If the character looks herm, tag again. Tagging what you see helps fill out the image, making it easier to search for, thus letting others find it.
Most arguments over tagging can be avoided by following this simple rule.
Do not tag using unicode characters.
Note: a character's backstory doesn't matter if they look female on one image and they ARE male on another. The point of tagging isn't to go digging to find out why tags are a certain way.
A general rule of thumb is to mark at least 4 basic tags on an image, some examples are:
See, you got a bunch of good ones already! Even though that is a general rule of thumb, it's always the best policy to add as many tags as you can see to the image; to make sure it's as complete as possible.
Note: Don't use the tags to propagate your own personal agenda or tastes. Doing so is tag abuse and will be strictly dealt with. If you have a problem, tell one of the moderators.
Please try to check the recent changes in the Wiki as well as forum discussions for current tag usage, at least once in a while. If you're unsure about a tag, think one is being used in a way it shouldn't, or have any other tagging questions not answered by the Wiki, don't hesitate to PM a mod or admin, or bring it up in the forum!