Determine each team's record against the other two teams. Rank the teams in order of best head-to-head win percentage.
Isolate the games between the three teams if the first tiebreaker didn't work. Determine each team's point/run/goal differential, depending upon the sport, against the other two teams. In those games, subtract each team's runs/goals/points allowed from what the team scored. Rank the teams based on best differential. For example, a team that scored 20 runs against the other two teams and allowed 14 runs in those games has a run differential of "+6."
If still tied, award the top spot to the team that finished with the best winning percentage within its own division, as compared to the other tied teams. This system is used when there are more than three teams in a division or teams are competing for a wild card playoff berth in a league that includes multiple divisions.
If still tied, schedule a three-team "round robin" tournament in which each team plays the other two teams again. The team with the best record in its two games earns the top spot. If tied, use point differential in the "round robin" games to separate the teams.
If still tied, flip a coin. All three teams have one representative flip a coin at the same time. The winning team is the one whose coin differentiates itself from the other two. For example, if the result of the three flipped coins is heads-heads-tails, the team that flipped tails wins. If all coins land on the same side, re-flip the coins.