The failover procedure depend on your storage system... Usually you have to stop the replica, promore the remote LUN and register the VM.
There is a product that can do all this work for you: VMware SRM (but it isn't free).
Or you can use other product like Veeam Backup or Vizioncore vReplicator.
Andre
Andrew | http://about.me/amauro | http://vinfrastructure.it/ | @Andrea_Mauro