This one is really fun & easy! You are going to teach your dog to touch something with his nose on cue. Do this because: it's fun, it's a good way to teach your dog to ring a bell to go outside, finishes, it can be used to desensitize a dog to nail clipping time, to teach agility, musical freestyle, & obedience trials exercises as well as for teaching service dog type behaviors.
Here's what you do:
Stand in front of your dog (or kneel in front of a little one). Rub some of your treats on the palm of your hand, so your hand smells good )to your dog!). Have the actual treats in your other hand.
Quickly bring your smelly hand, empty, palm forward almost right up to his nose. I guarantee the first time he'll poke it, hoping it contains that treat he smells. Super! He touched you! C&T (Click & Treat), giving the treat from your other hand. Be sure you clicked just at the exact moment he touched your hand! If you aren't in time, don't click at all, just praise.
Do it again & again, gradually moving your hand a bit farther back so eventually he is reaching out or walking to touch it. But do it gradually - over several sessions. I knew my Rottie Teddy had the concept when she would reach out to touch my hand, but keep eye contact with me the entire time.
Now... at the seminar where I learned this from trainer Leslie Nelson, she said that many dogs will do this excitedly about 6 times, then lose interest & just look at you. Don't quit - just perhaps rub a bit more treat smell on your palm.
You can add the aignal (or "cue") pretty quickly because the behavior is so easy. As soon as your dog isreliably touching your hand when you offer it, begin saying "Touch!" as you put your hand out.
Next steps are to have your dog touch your other hand instead and start to become variable with rewarding.
You can also then use the signal "Touch" to mean touch other things. In our classes we use it to teach dogs to go lie on their beds, and at home my daughter taught Sugar Bear to ring some bells hanging from a doorknob as a signal that she wanted to go out. Very useful behavior! Sugar Bear can also pick up something I drop, get me a tissue when I sneeze, and push an Easy Button - all taught with targeting.