Search exercises are my favourite way to work my dogs. They love the challenge, I love watching them and it tires them out completely. The trick is to keep the searches on the right level of difficulty. Not too hard, so they give up and not too easy, so they don't feel challenged.
Start by using small, small pieces of a treat that your dog really likes. The pieces shouldn't be any bigger than raisins (your dog shouldn't get full up on treats, just get a taste of them). Go to a lawn with short cut grass. Sit your dog down next to you and spread out a few treats in front of your dog - say "find" and let the dog go. Let your dog find and eat his/her treats. Do the same thing again, but now expand the area a bit. Continue in the same way until you can spread the treats as far as you can throw - without your dog loosing interest and giving up (this might take a couple of days training).
I hope that your dog likes toys, as it is needed for the next exercise. Take your dogs favourite toy out into the garden, sit your dog down or have someone hold him/her, as you go out and place the toy with a small treat underneath it, on the lawn. Your dog will find the toy using his/her eyes in this stage of the training, but it doesn't matter. We want to take it slow, so your dog will know exactly what we expect him/her to do. Go back to your dog and say "search" and let your dog go. As your dog finds the toy, run out to him/her and praise him/her and play around with the toy on the spot your dog found it. Repeat this exercise, making it more and more difficult for your dog to see where you are placing the toy. If your dog seems really interested in this "game", you can try and cut out the treats.
To take the exercises a bit further (when your dog can do the above exercises), you go out on a field with high grass and do the exercises again from the top (small area, let your dog see where you drop the toy or treat) and from there you can just continue to expand the area you work on. When your dog gets really good at finding the toy in high grass, you can start throwing the toy out in the field (this is why we train your dog with the treats that are thrown out).
When a dog is searching for something, it should be using it's nose up high and go by the scent that lies in the air, rising from the toy (where ever it is). When a dog is tracking it is supposed to use it's nose down to the ground and follow a track of smell that is left behind by the person or animal that has walked there.
A good measure to have, is to do an exercise 3-4 times in a row, and then give the dog a break for a couple of minutes. But when you do as tiring exercises as tracking or search, you should keep the training down to 3-4 searches/trackings per day. We don't want to make the dog confused or bored.
It is also good to vary the exercises, try to avoid doing the same exercise every day, in the same place, over and over again. The dogs need to feel stimulated in their work, just as we do in ours.
In all training, be sure to vary the type of treats you use, the environment you train in, the type of praise you use (treats, pats, your voice, a toy). However, when you are just beginning a new exercise, you should remain in the same environment until you are confident your dog knows what you expect him/her to do. When your dog knows an exercise well, you can cut out the treat and just praise your dog with your voice. If your dog is keen on toys, it is even better to use the toy as a reward instead of treats, as the dog can get overweight if you train him/her often!