The below video shows a great work out and also more importantly a great way to improve the footwork.

Taken from Andy Murray's fitness trainer Jez Green, its called the 8 shot grid.

This is a training drill which incorporates all of the basic footwork patterns in baseline play. A player can use this grid to shadow the split, mogul, power, hop through and drop steps as described in our cutting edge section until they are performed with perfect balance and perfect foot placements.