In the trick training article "Go to Your Mark", I explained how to teach your dog to go to a specific item - such as a small piece of carpet or a low stool - and place his front paws on it.
This is a type of target training because your dog is to go to a specific item - a target - o perform his trick. There are other forms of target training too, in dog sports as well as trick training. Its multiple uses make this a potentially valuable, as well as fun, exercise to teach.
The first target you'll use will be the flat of your hand. When your dog knows that well then you can use other items depending on what you want to do with your dog. If you do agility, target training can teach him to hit the contacts on the agility equipment. If you're doing obedience, therapy dog volunteer work, or just having fun with trick training you will find other uses for target training.
You will need some treats your dog really likes. Ideally these are treats he doesn't get on a regular basis. Keep in mind your dog's sense of smell is his most important sense, so choose treats with an enticing (to your dog) smell. Swiss cheese diced into small pieces works well as does freeze dried liver.
Ask your dog to sit in front of you. Hold one hand out, open, with the palm toward your dog's nose and with the other hand, hold a treat immediately behind the open hand. Slowly move your hands towards your dog and when his nose touches your open hand praise him, "Good!" and pop a treat in his mouth. Repeat five or six times and take a break.
Repeat this for several sessions. When your dog begins to move his nose towards your hand on his own, without waiting for your hand to come to him, praise him and give him a treat. The next time you repeat this training step, tell your dog, "Sweetie, touch!" as he touches your hand.
Gradually decrease the distance you move your hand towards your dog's nose and encourage him to move toward your hand. Ask him to touch you at the beginning of the exercise rather than waiting for him to touch your hand.
Then, when he's touching your hand with his nose reliably, add some variations. Move your hand slightly to the right, or left, up or down. Use your voice to encourage him, cheer his efforts, and a quick treat to reward him for moving. Keep the training sessions short and fun.
When your dog is targeting your hand well, you can add another target. Start with a small one, such as a ball, and simply hold the ball in your hand, repeating the training steps above. When your dog is touching the ball in your hand, then place the ball on a surface and keeping your hand behind the ball, ask your dog to touch it. Praise and reward him. Then gradually move your hand away.
Then you can start adding additional targets. These can be things around the house, such as toys, or can be items to be used for other tricks.
Don't forget to have fun with this (and all) trick training. If you want to amaze your friends, teach your dog to touch a water bottle. Then when friends are visiting, line up several items with a water bottle in the middle of the row. Ask your dog to touch the water bottle. People will be in awe of your brilliant dog.