Some tips:
Any time someone sends information by email that really should be in a wiki, make a page for that topic and add what they put in the email. Then reply "Thanks for that info, I've put it into the wiki here so that it's easier to find in the future."
Likewise, if you have information you need to share that should be in the wiki, put it there and just send an email with a link to it, rather than email people.
When you ask people for information, phrase it so that putting such documentation in the wiki should be considered the default or standard: "I searched in the wiki but I couldn't find it. Have you put that info up there yet?"
If you are the "wiki champion", make sure other people know how to use it, e.g. "Did I go through how to create a new page with you yet?"
Edit the sidebar to make sure it is relevant to your work.
Use "nav box" style templates on related pages for easier navigation.
Put something like {{Special:NewPages/5}} on the front page, or recent changes, so that people can see the activity.
Take a peek at Recent changes every few days or week, and if you notice someone adding information without being prodded, send them an email or drop by and give them a little compliment.
