SBS 2003 to Server 2012 Standard - Migration Protocol

We are planning to move from a Small Business Server 2003 to Windows Server 2012 Standard.

We will run both server hardware in parallel during the transfer, then once the new 2012 server is up and running we will throw away the 2003 SBS Server.

We only need active directory info, we do not need Exchange or SQL data as this is not used.

What is the protocol for transferring the active directory domain information across to the new 2012 server?

There is a rather extensive piece of product documentation covering the migration scenario of an SBS installation Essentials 2012. It includes the activation of a "migration mode" on the SBS server where you would be able to transfer FSMO roles to the new server without the SBS mocking about it.

But as you are just interested in the AD user data and are not using the Essentials product line, I would not bother all that much. Just promote the Server 2012 as a DC to the domain (the Schema will be irreversibly changed in the process, make sure you have a backup to be able to revert to if anything goes wrong). Contrary to what you read in the documentation, you can transfer the FSMO roles off the SBS 2003 DC just as long as you trigger the transfer from your new DC - this is something you can do at any time in your migration process. Of course, you also could choose to switch off the SBS and seize the roles after you're done with the data migration.

Moving the file and print shares is no different from any other file server migration, the FSMT and the Print Migration Wizard might be of help here if you have a lot of shares / printers to migrate and care to read the accompanying docs instead of just re-creating the share config from scratch (might be faster if you have just a handful of shares and no complex ACLs on them to care about) and copy the data over using robocopy.

After you are done, you should be cleaning up the garbage from the SBS 2003 install - especially check if the logon scripts still apply and if the group policy objects from the "SBS era" are still appropriate or should be modified or deleted.