Reinforcement through repetition is another way to get people to use a wiki. Once you declare that the wiki is the preferred place for certain activities and content, then you need to stick to that process.
This means that at the start you may sometimes have to take things sent to you in email and transcribe them on to the wiki. However, making “put it on the wiki” a repeated refrain within your community will eventually make the wiki the automatic destination for information. This also has the side benefit of drastically reducing the contents of your email inbox.
Up to 60% of business documents just end up sitting as email attachments (many unopened). Putting things in one central place on a wiki makes it easier to find them. It also makes it easier to recover information, since your wiki should be backed up.
If you use the maxim that “if it’s not on the wiki it doesn’t exist,” it will make the wiki the default place of record, and usage and contribution will follow.