Below a few basic commands with whistle signals, but of course you can choose your own whistle signals.
Lie Down: (or Af) This is "the emergency brake" for the dog. A border collie can fall off in a few seconds. Some dogs only stop walking for a while. At "Lie Down" some dogs remain standing, often with a low head and a bit lowered by the front legs. This is also allowed, it is a 'stop sign', as a result or which the dog does not continue.
Walk on: (or Walk further) Hereby the dog walks straight towards the sheep. This command is used with both the fetch and the drive. An advanced Border will make its own adjustments to keep the herd walking in a straight line.
Come bye: (or Left) The dog runs around the herd (clockwise). You must view it from the dog's position. This is a bit tricky in the beginning, but you learn that pretty quickly.
Away: (or clockwise) The dog runs (counterclockwise) around the herd. Here too you have to look at it from the dog's position.
That'll do: (or Done) This is the command for stopping work. The dog must come here. The work is done!