The three which are always required are:
- Web Application User
- Session Service
- Session Central Service
The one which is optional dependent on installation options is:
- Management Console Application User
This last is only required if the Management COnsole is installed to a different web site to the web client.
To create the service accounts, you need to be logged onto the Domain Control (in my case DC1 which is running Windows Server 2008 R2) and open Active Directory Users and Computers.