Once you have taught the focus and the sit, you may find that the dog is close to being in the front position. This position is easily taught with luring; you place both hands in front of your legs at the dog's mouth height and walk backwards a couple of steps and stop, once the dog is close to you and straight, you can reward with the food. Once they are doing this easily, lift the food so that they end up in a sit. Then you can add the command, typically "Hier" in Schutzhund.
Keep in mind that, in teaching the front, the competition points are in focus and a straight, close position. You should be able to easily reach down and touch your dog without having the dog flinch or shy away from your hands. If your dog is sensitive to your touch at this stage, take the time to teach him that it is ok for you to touch him while he is in position. To do this, start very slowly with your hands around his face (not actually touching him) and then move forward slowly over time and do many repetitions rewarding the dog for maintaining attention and not shying away. This is important to teach because you will face a problem later with the retrieve if the dog is sensitive to touch in the front position.
The next step is to fade the hand signals. You can move your hands apart gradually until they are at your sides in competition position. The next step is to complete the whole recall, in Schutzhund, this must be fast. Speed can be built by getting a friend to hold your dog, tease him with a toy and run away making excited noises, call the dog, and have your friend let it go, continue running and present the toy as they get close. Alternate giving the toy before the dog reaches the front position and occasionally helping him into the straight, correct position, before releasing and rewarding. Ideally the reward should be presented at the spot that you want the dog to end up, many people like to put a toy under their chin or though their legs but do be careful with this, an 80lb dog at 35 miles per hour can hurt!