Wiki specific ideas to prevent conflict within the existing community should go to CategoryConflict.
Create RecentVisitors or CategoryHomePage and invite users to add themselves, click on the newly created link and write a sentence or two about themselves. For the user, this is interesting and it satisfies the ego -- they are creating a homepage for themselves. For the wiki, this introduces basic wiki features like page editing and page creation, and it asks the user to commit a bit of energy to the wiki. Chances are that the user will remember this effort, bookmark this site, enjoy the experience.
See FrontLawn for more about this.
Most wiki newbies don't know to put the CategoryHomePage tag onto their first page. Usually the editor does this for them. This is the first personal contact with the potential new user; use it well. A personal greeting of some kind may be appropriate. "Welcome aboard!" or just a little "Hi there!" will give new users a warm and cozy feeling inside. It's the personal contact that counts.
See WelcomeNewcomer for more about this.
When the editor greets new users, sign the greeting with the username. This will create a link to the editor's homepage. If the editor maintains an OnlineDiary or a similar source of personal information, new users following this link will feel surprised by the amount of personal information revealed. This will prompt many users to similarly add more information to their own page. This means more commitment.
People like to get constructive feedback about what they write. Encourage them to write by growing the wiki around a new user's contribution:
See also Rheingold's TheArtOfHostingGoodConversationsOnline.