Start by drawing a grid on a board and labeling the lines with numbers in the way you would for the first quadrant of a Cartesian coordinate system (start with 0 and increase by 1 each line over). Put markers for each student in the class at separate points on the grid. Tell the students they are on an island and must find some buried treasure that is buried at certain ordered pairs on the grid. Have a list of ordered pairs that represent the positions of the treasures, but do not let students see. Let students take turns moving their markers one unit in any direction. If the student lands on a treasure, let her know and give her a small prize. Ask students where the treasure was (elicit responses in the form of ordered pairs, such as (1,3) and (4,4)).
Give students maps in the form of grids (you can draw a grid over a cartoon map or find similar material online). Have students work in pairs. One student will give directions (e.g. go up three and left one), while the other student will move his marker on the grid. Students can practice using the terms of ordered pairs to state their position (e.g. "we moved from (4,2) to (4,1)").
Have students draw a map on graph paper. The graph paper, acting as a grid, gives students a large area on which to draw. Some ideas for maps are maps of the classroom, maps of their bedrooms or maps of a well-known fictional area (such as in a video game or TV show). When students have finished drawing their maps, request that they place ordered pairs on the important points of the map.
A classic game of battleship can get students talking in terms of ordered pairs. Battleship is a game played on a grid. Two students place ships that take up a number of ordered pairs on the grid, depending on the length of the ships. Students take turns guessing the positions of their opponent's ships by saying ordered pairs. If a student guesses right, the ship is said to be struck. When all of a student's ships are struck, that student loses the game.