How can I automatically have a node become primary in an Availability Group? In my environment, I have Db01 and Db02 setup with SQL 2012 AlwaysOn. Db01 is the preferred master as that is where all of the backup jobs reside. Typically, the only time that Db01 is unavailable is during maintenance period of installing Windows Update. 

Is there a way to always have Db01 be the primary when it is a member of the cluster? Currently, when Db01 rejoins the cluster after a reboot, it is marked as the secondary, since Db02 has become the primary. I would like to see Db01 join the cluster and then automatically (or via a command executed on startup) be designated primary.

Db01 and Db02 are both set to SYNCHRONOUS_COMMIT and Automatic Failover Mode
You need to set that in the AG ROLE properties as below :

Windows server 2012