To win in Ultimate Tic Tac Toe, players need a combination of long-term strategy and the ability to control each small board. First, always think ahead several moves instead of focusing on an immediate victory on a single square. Each of your moves will determine which area your opponent has to play next, so try to send them to disadvantageous boards or boards you already control. Taking control of the center of small boards often provides a significant advantage as it opens up many flexible attack and defense options.

Additionally, you should prioritize creating multiple winning opportunities simultaneously to put pressure on your opponent, forcing them to defend rather than attack. Don't neglect defensive tactics, as even a small mistake can allow your opponent to control the entire board. Observing the entire game instead of just looking at individual boards will help you maintain the initiative. Finally, patience and the ability to read your opponent's intentions are key to mastering the game and winning.