How is home-field advantage determined for the MLB League Championship Series and the World Series?
By rotation. Each year, the divisions are ranked 1-2-3; in any series, the team from the higher ranked division has home-field advantage. A wild card team can never have home-field advantage in the league playoffs. The wild card plays the division winner with the best record unless they are in the same division. In that case, the wild card team plays the division winner with the second best record. The leagues alternate home-field advantage in the World Series.