As moderator, you are your Wetpaint site's welcoming committee. Every newly registered user should receive a welcome note from you on their profile page, preferably within 24 hours. You may want to encourage your other moderators to do the same, as this will entice new users to return to the site. Too often, people register with a site on a whim and do nothing else in the community. If they are made to feel welcome and relevant, then they will have more reason to make themselves at home on your Wetpaint site.