Points are seperated by :, and can either be a plain text address, or (lat,long). Transit requests will only work for two point entries.
Options for directions can be found at the google maps API.
A good test of options is using 'optimizeWaypoints:true' and setting several waypoints in a non-logical order; going from London to Moscow to Paris to Berlin is a good example. If optimize waypoint is true, the map should automatically reorder the waypoints(NOT the start/end points) to give the shortest possible route.

Relevant section of the Google Maps API: Directions