Ask the students to play the game in pairs. Challenge them to find a winning strategy. As they play, circulate around the classroom and ask them what they think is important.
After a suitable length of time bring the whole class together and invite one pair to demonstrate their strategy, explaining their decisions as they go along. Use other ideas to refine the strategy.
Once students are confident about their strategies they could move on to exploring what happens when the game starts with four or five dots.
Does it matter who goes first?
Why must the game end after a limited number of moves? How many?