Anatomy of a good PbP game

As many of you know, we are working through a pbp game on the Network, going through some of the old modules, with some slight changes.  I am interested in hearing ideas on what works best for pbp when the action starts, such as die roll conventions, etc.  Best ways to integrate them, and work them in.  Including best ways to address and handle xp awards, character advancement, and dividing responsibilities for keeping most recent characters posted current.<div>Also interested in any house rules, or things you generally think makes a PbP engaging.  I am looking forward to learning from your collective wisdom.  </div>