Configuring the User profile service application - User Profile Synchronization Service stuck on starting

OK so I thought it was about time I cleared this one up for my own sanity.

As described in my post User profiles in SharePoint 2010, the User profile service application is required to sync user information. A well known issue when configuring this is that the the User profile synchronisation service actually gets stuck on activation. It just says:

"User Profile Synchronization Service - starting"

N.B. The service probably isn't stuck. It is just retrying to start a number of times.

The following points might help you get through without error.

• Use a farm account to run the service. Potentially use the same account as installing.
• Add this account to local administers group whilst setting up the service. This can be removed later and will only need log on access.
• Ensure that the user account which is being used can read Active directory (assuming ad is source). The account requires the "Replicating directory changes" permission in AD. This was new to me so pointed our infrastructure guys at http://support.microsoft.com/kb/303972 to get them to add the permission at domain level and include all descendants. This will allow the service to access.
• Ensure the managed metadata service is running.

With a bit fortune on your side you should be up and running.