Parts of my answer to this question would apply: lots of communication.
If you can, put together a small group of people who are friends as well as "normal users" in the company. You want people who will tell you if you're doing something wrong, or who will let you know if they hear other people grumbling about something your group is or isn't doing.
Use all the standard communications tools: newsletters, emails, IT web site, training sessions, seminars, and encourage feedback. Ask people to respond to emails and newsletters. When you give talks or seminars make sure there's time to take questions.
For managers, you need to talk to them one-on-one as much as possible. Get their feedback whenever possible and respond to it: make sure you're providing the services they need.