In a standard domino game with 2 to 4 players, you typically start with seven dominoes each. This is the most common starting hand size for beginners. However, for more strategic play, especially in one-on-one or three-player games, players may start with nine dominoes. With four players, each usually gets seven dominoes because the standard set contains 28 dominoes in total. So the usual starting number is either seven or nine dominoes per player, depending on the specific rules and number of players.