not sure whether it is a leave or a drop cue that you want, but i just posted this on another thread about "leave" which i class as the dog leaving something it has not already got but is making a bee line for.
Hope this is of use.
Teaching leave
Have a piece of food in the palm of your hand; show this to your dog. He will be interested and possibly try to grab the titbit.
As he moves forward to take the food close your hand making the food unavailable.
You should keep your hand still rather than pulling it away.
When the dog gives up ‘mugging’ your hand and backs off give the cue leave it, open your hand and give him the food using your other hand, along with the cue ‘take it’
Repeat this several times until your dog realises that it is pointless to grab the food.
Build this up so that the titbit can be visible for several seconds before the dog is rewarded.
It is important that you do not allow your dog to help himself to the reward, he must be given it from you and always from the other hand that he has been told to leave.
It is very important that you use the take it command as you reward, this conditions the dog to come back to you for the reward, rather than snatching up the ‘forbidden food’.
Start rewarding the dog from your pocket or somewhere other than your hand.
You might want to use your treat bag.
Progressing the leave
We need to move this on because in real life your dog will pick up items from the floor that we need him to leave so this is how we get dogs to leave stuff on the floor.
Food on the floor is perceived in a different manner by the dog.
Lower your hand toward the floor, and in several different directions. Repeat the above, and then move it into another room, outside--wherever you can.
It takes a while for the dog to learn to "generalize" the behaviour.
Just because he knows how to "leave it" in the kitchen facing north doesn't mean he will understand he has to also do it in the bedroom facing east.
So you back up a few steps, re teach the behaviour in each new environment, setting the dog up for success.
This usually takes only a couple of clicks to get the brain in gear in a new environment.
Once you can lower and raise your hand and the dog will back off, put treats on the floor and watch closely!
Now is when the chowhounds think "free meal" and will jump on it.
Be ready to put your palm OVER the treats.
You don't want the dog to get those treats because if he does, it is very strong "variable" reinforcement.
What does that mean? Well, variable reinforcement is something that happens not every time, but it has happened before and probably will happen again.
Like a slot machine. You know when you put your 10 pence in, each pull of the handle won't net you a payoff.
But you have gotten a payoff before, and you suspect you will again, so you keep on chucking in those 10 p’s and hoping the bars will come up with three cherries. That's the power of variable reinforcement.
So, you don't want your dog to get those treats on the floor!
Keep repeating the "leave it" and click and treat, never allowing the dog to have the treats on the floor, but only the other treats you will give him from your hand.
This all goes very rapidly, and within 15 minutes you should have a pretty good behaviour going the first time you try it.
Again, once your dog is effectively ignoring treats on the floor, you can make things harder and walk him by the treats, saying "leave it" before you get to the treats on the floor.
But be careful: don't tighten up on that leash involuntarily and make 'leave it' a punisher. The dog needs to make a choice, and make the choice you want him to make. He will, if the reinforcement is strong enough.
You will be happy when you can stop your dog from investigating the garbage, faeces, a dead animal, or a box of mouse poison, so take the time to teach your dog to “leave it.”
The way to success in teaching your dog tricks is patience, practice, praise, and persistence. Every step in the right direction should be rewarded as though she has just won the lottery. Tricks are fun – learning how to do them should be fun, too.