Workflow where manager is sent approval/denial

Our setup is 4 domains where the SD and Workflow live in one domain and the users live in the other three.  I'm creating a HW request form using the ServiceCatalog.Request.Template where the approval needs to automatically look up the users manager and send them the task to approve/deny.  I really don't even know where to start with this.  Any suggestions to where I should look for examples or even giving me an example would be awesome.