On the first round, the first player reveals the first tile of each stack. There is only one serie of 4 tiles. He chooses one and discards another.
The second player then chooses one of the remaining two and discards the last one. He will be first player for the next turn.
On the second turn, 2 series of 4 tiles are revealed. The first player selects one of the series, then picks one of its tiles and discards another. The second player then chooses one of the remaining two in that series and discards the last one.
The first player changes each turn, and a new series of 4 tiles is revealed, so that there will always be 2 series of 4 tiles available to choose from – except on the last turn, where there will only be one series left.