well if you havent been developing long enough Project Admin wouldnt be the best thing, also if you havent been part of a project to begin with being an admin should be avoided its just looking for a disaster.
I was in a small project which the project leader really didnt have much idea where to go with the project, and wasnt really competent with various things involved such as design, programming etc. Since this person really didnt have much clue and in the end because of it become agressive I left the project.
So firstly what Id do. If a project has been past on to you only accept if you have been part of the project. It allows quicker transfer between admins, allowing the new admin some idea where the project is heading.
You dont need to be a genius in all areas of the project but having some basic concepts of each section e.g. graphics would be something good.
Another good thing is to be assertive and make sure everyone knows your in charge however not being agressive or passive. So make sure you listen to what developers say and not just ignore something.
The project I was in we used AIM and MSN, it was a relatively small group so a consensus on what should be used was relatively easy. However I think communication will be determined by the amount in the project. I wouldnt use AIM, MSN etc for a group with over 8 involved a Forum would be better however getting into quick contact still will be required maybe still using AIM, MSN for smaller development chats isnt too bad.
As for Documents, the team I was in didnt really have much in documentation it was basically an overview of what was to be done. This will also depend on the project and if you wish to have time constraints.