Add easy to spot guidelines for tag creations. Maybe a searchable list over currently used tags to.
As I see it tags are meant to provide a more detailed subject search than the forum categories, but less detailed than full text search. This is a great idea.
The problem, however, is that the poster him/herself are creating the tags, and people are different, and english contains lots of variety. Result is that we end up with lots of different tags that descripe the same (eg. games, game.) and a large difference in level of detail.
I must admit that I don't know exacly how tags are handled here. Maybe the search has a build in list of synonyms, and also "stem" the tags. If so this is less important, but a guide could still be usefull. (eg. to motivate posters)