I have been assisting several teachers set up wikis for their classes next year. Some of the issues that have come to light….
1. make sure they right down all their passwords and somewhere they can find them again!!
2. Check with the network manager to ensure emails from the wiki are not blocked by the school. This was a particular issue for us.
3. Make sure that each person has a clear idea on what they want the wiki to be. I have recommended blogs to several staff who were really looking for journal type application rather than a learning space.

This is a link to the Wikispaces learning A to Z page. Here are many educational wikis which can give an idea of how wikis can be used in education: