Currently under tags edit box there is only this info:
Combine multiple words into single-words, space to separate up to 5 tags (voting bug)
I think it should have more hints to prevent creation of new, improper tags all over again.
A message dissuading people from creating new tags would be a good idea, perhaps "Try to use appropriate existing tags before creating new ones"
Also perhaps mention of how to pluralise tags, say
Even just a few examples (and anti-examples) would be good. The retag thread is full of such ;-p