One of the main questions needed to be answered is whether or not this RP has more activity through forum posting, or through AIM.
For forum role playing, all of it is localized, and easier to manage. There will be few questions/confusions, and there are less necessities required to participate.
For AIM roleplaying, a common instant messenger is required. All players need to be available at a similar time for the roleplay to work. However, it will also move along much faster.
A mix can also be implemented, but it must be decided what would take place where.