Teaching a voraus begins with a target point, you can use a food bowl, target stick, ball hung from a tree or pole, a mat or a favorite toy.... Start with a short distance (5 or 6 feet), begin by putting the dog on a sit or down stay and putting the target out while they watch. Gradually increase the distance of the send. When setting the dog up for this exercise, I like to heel to the center of the field, then say "sit", then place my hand by the dog's head and let him see the target, typically I will mark when he looks at the target with a simple "good" said in a normal tone. With young dogs, I might then hold the collar and speak excitedly, when they are barking or pulling forward, release at the same time as the "voraus" command. This should help build some drive or excitement for the activity. Later on I will send without building drive, and then add some heeling. When adding the heeling, I will typically still stop prior to sending to begin with. I can always add drive or excitement back in later in the same manner or by using a more exciting toy, one of my females loves squeaky balls.
Once the dog can run the entire length of the field, we begin putting the target out before we begin training, before getting the dog out of the car. The first few times we do this, we start the dog much closer to the target point again. Then we start to fade the original cue with the hand by the dog's head because we cannot use that in trial.