One of the scenarios that helped the Ravens toward a bye happened last night, when Houston lost to the Indianapolis Colts. Now, the Ravens can capture their first division title and first-round bye since 2006 if the Steelers fall to the two-win Rams at home.
The New England Patriots can also secure a first-round bye if they beat Miami at home Saturday. If the Ravens win out and the Patriots lose once, the Ravens would likely take the top seed based on strength of victory (the Ravens and Patriots would have the same record in the conference and with common opponents).
You can run all of these scenarios and more with ESPN's playoff machine.