Make notes: Note down key information ie name of other driver(s), contact tel numbers (landline no. is better than a mobile), registration number of other vehicle (very important), insurance details if known.  Record any known witness details.

Take photos: It is a good idea to take a few photos of the scene and aftermath - photographing the vehicles involved (with permission) and their positions on the road, can be very useful.

Call your insurers: Get your insurers involved asap and record he incident with them.

Call a road accident lawyer: if you have been injured in the accident or have other legal queries / problems that cannot be handled by the insurers.

Police involvement: You may choose the call the police but they are infrequent visitors nowadays to most road accident scenes. They will attend any accident where people are injured or an ambulance has been requested. They will also attend where vehicles are causing obstruction to other road users. Generally though, for minor incidents the police do not attend and do not need to be called provided that the parties involved cooperate with each other and abide by the basic legal requirements following an accident.