There's one "game" I start with all my dogs that come into the house. It's great for nose work and gets them really excited to play.
I take a handfull of boiled chicken, some boiled liver and add it to a blender. Then using vegie stock, or even water, I fill it up the rest of the way. Blend really good so it's totally liquid. Then I use a sports bottle with a squirt tip. Fill it up with the liquid and take some bits of the chicken an liver and head outside. I will do short squirts on the yard from a foot to long squirts and then end the squirted line with a bit of the meat. I may have 5-10 trails all over.
Then I let the dogs out! Whoa! What a trip to watch! You see them following each trail and then snag the treat! There ya go.....the beginnings of a nose work game.
Once the dog is tired of it.....you can then take a rock and place it over the treat at the end of the squirt line. Takes them a few to figure out how to move the rock to get to the treat.
You can then move to putting treats under boxes. And shake them up a bit by only putting treats in a few boxes, not all of them. They learn which box to work on and which to pass on. Start using the command "Go find".
Then you can do this inside the house without the squirt trail. Just boxes with a few holding treats. This is a great "give me some time alone" game. You will have several minutes of peace! LOL
If you really want to get more into it.......get yourself a key ring with a container on it, like the mini-tupperwear container one. Or even a rabbit's foot will work with some modification.
Put the treat and the keyring into the box together. Start to use the command "Go find keys". The dog will learn to associate the treat with the keyring. When they find the treat and keyring, you can praise with "Good keys". Then the "Go find keys" training begins. Whoo hoo! Now that's a functional game!
Start to put the treat inside the keyring. If you have a rabbits foot, take off the metal cap, drill a hole into the center and put PB inside it. Put elmers glue inside the cap and then reattach it. Let the glue dry before you start to train with it. Just rub a little PB on the fur part to get the nose working harder in finding it. Like a teaser.
Put the keys inside a box. Have several other empty boxes. Then command "Go find keys". When they have it mastered, then add one key at a time. Doesnt have to be a key in use, any key will do. Slowly add more keys. When the ring is full like your set of keys you use.....teach the "bring keys" command. You want the dog to bring the keyring to you. Give lots of praise and treat with whatever treat you placed inside the key ring.
Now you want to start to hide the keys throughout the house. On tables, under tables, in the couch, in coat pockets, etc. Anywhere that you may find lost keys.
Now you have a S&R dog for your lost keys! LOL