A good stalker can move silently anywhere, even through undergrowth and across stony ground. Here are some ideas for a training course to help you practice.
Set it up somewhere secret with other Good Spies. Take turns to be the Trainer. The Trainer stands with his back to the course while the others, one by one, try to creep up and touch him. Each time he hears a noise, he calls out and the stalker loses a point. See who loses the fewest points while stalking.
Lay planks across some bricks. Scatter stones on them. Each stalker tries to walk them without rattling the stones.
Tie a string between two sticks stuck into the ground. Hang pairs of tin lids from it, so low you have to flatten yourself to creep under.
To make these clanging lid pairs, tie a piece of string round each tin lid. Knot it and hold it in place with bits of sticky tape. Hang the lids on the string, quite close together. Then they will clatter if one of them is touched.
Arrange some tins across the course so that the stalkers must move very carefully to walk past them. Stack the tins or put a few stones in them so they rattle if knocked.
Cover stretches of ground with things that crunch or rustle, like gravel, twigs, dry leaves or newspaper.