how the NFL does it
http://www.nfl.com/standings/tiebreakingproceduresDETERMINING HOME-FIELD PRIORITY
1. To determine home-field priority among division titlists, apply Wild-Card tie breakers. 2. To determine home-field priority for Wild-Card qualifiers, apply division tie breakers (if teams are from the same division) or Wild-Card tie breakers (if teams are from different divisions).
TO BREAK A TIE FOR THE WILD-CARD TEAM
If it is necessary to break ties to determine the two Wild-Card clubs from each conference, the following steps will be taken.
1. If the tied clubs are from the same division, apply division tie breaker.
2. If the tied clubs are from different divisions, apply the following steps.
Two Clubs
1. Head-to-head, if applicable. 2. Best won-lost-tied percentage in games played within the conference.
3. Best won-lost-tied percentage in common games, minimum of four.
4. Strength of victory.
5. Strength of schedule.
6. Best combined ranking among conference teams in points scored and points allowed.
7. Best combined ranking among all teams in points scored and points allowed.
8. Best net points in conference games.
9. Best net points in all games.
10. Best net touchdowns in all games.
11. Coin toss.