It really depends. I think in all my leagues (all 7 were hosted by yahoo

) this year we decided to use the yahoo default tiebreaker system. Here's their system:
yahoo default tiebreaker system wrote:In the event that a playoff game ends in a tie, the deadlock will be broken using the following system:
1. Most touchdowns scored by entire starting roster.
2. Most fantasy points by starting quarterback(s).
3. Most fantasy points by starting defensive team(s).
4. Most fantasy points by starting defensive player(s).
5. Most fantasy points by starting defensive back(s).
6. Most fantasy points by starting defensive linemen.
7. Most fantasy points by starting wide receiver(s).
8. Most fantasy points by starting running back(s).
9. Most fantasy points by starting tight end(s).
10. Most fantasy points by starting kicker(s).
11. Random "coin flip".
I've also seen leagues use most overall points during the regular season, most bench points for the playoff game, head to head record in the regular season, and many other tiebreakers. The key is to have a tiebreaker system set before the season starts. Ties are rare but you need to be prepared if & when they happen.
Good luck!