Migrating from Exchange 2003 and Windows server 2003 to Exchange 2013 with Windows server 2012

Hello,

I have to migrate a windows server 2003 (AD) and the Exchange server 2003 to Windows server 2012 with exchange 2013.

I want to know, first of all, which migration should be first: the AD or Exchange?

anyone can help me with a "list" of steps I must do? (only the steps, at least, I will handle then with the rest of operations.)

Thank you,