Plotting points on a coordinate grid
Start at the origin, the corner where both axes read 0. The first number of the pair tells you how far to walk along the bottom; the second, how far to climb. To plot (4, 7), go 4 across, then 7 up, and mark the point where those lines cross. Points go on the lines, not in the squares, which is the most common early mistake.
Mystery pictures
A favourite exercise: give a list of points, have students plot them in order and join the dots to reveal a picture. Use 0 to 20 for pictures with any detail, and print one grid per page so the drawing is big enough to colour.
Need negative numbers too? Use the four-quadrant coordinate plane.