Stand on one leg, and try to keep your balance.
Be careful and hold on to a wall or table for support when you first start this exercise, but as you feel more confident you can reduce contact and support from the wall or table.
A single leg balance exercise such as this is a brilliant exercise, it has huge benefits including strengthening the muscles and ligaments around the ankles and knees, and improving balance.
Try and build up to holding the balance for 60 secs