When and how to create new tags

Question

I often hesitate to create new tags, as I'm afraid that the tag will only be used in that one question. On the other hand, it is hard to tag some questions with the existing tags.

Is it correct to be cautious when creating new tags, or should I feel free to create one whenever it makes sense?

And if I do create a new tag, does it make sense to search for that keyword and tag old questions with it if it makes sense? Here I'm worried that this will be quite a lot of minor edits, which may spam the front page.

The question that brought this up for me was this one, which was tagged with plugins, which didn't make sense to me. I think fitting tags might be metadata and image, both of which seem to be appropriate tags for a lot of questions (I was a little surprised to see that neither exists yet, so maybe they are not appropriate tags?).

Answer 1

Your question is indeed valid - most people either misuse the tags, or misunderstand the concept completely.

Usually, you should prefer existing tags, where it makes sense. Rarely, a new topic surfaces, and it makes sense to create a new tag that was not used before. It is rather ambiguous to give you a complete guideline, but it's kinda like "I'll know it when I see it" - it really just comes after being familiar with the existing tags, and how they are used.

I would suggesting looking at some tagging posts here on meta, and on Meta.SE for the philosophy of tags... A common mistake is to use "meta" tags, i.e. tags that describe the question, instead of the topic being asked. Another mistake is using tags to add information that is not present in the question as asked, or using tags to make the question "special".
(Ideal usage of tags is categorization and search optimization, nothing else).

Now, in your specific case - at first reading, I thought the question really WAS about the use of the plugin, and not specifically about images or whatnot. But both existing answers seem to have thought otherwise... So basically, I would say that without any tags, the question is definitely unclear, and needs to be clarified by the OP.
The fact that the OP tagged it with "plugins" seems to hint in my direction, BUT that is a misuse of the tag, and I would choose not to rely on it. Regardless, there is obviously missing information, and as such I do not actually know how it should be tagged.

(P.S. in the future, please try not to edit a question just between acceptable spellings, "plug-in" is just as valid, as are British spellings ;-) )