Tonight I had an interesting experience working with a client. We were working on recall with a dog who had been doing great around the house and in the yard, but when she was out at the the Normanskill farm the call of the tall grass and what was hiding there was too strong and she would not respond to anything. We had ham and turkey for rewards and she could not have cared less.
We took her into the mowed, fenced in area to see if that would help ease the distractions, and after some trial and error realized she would come when we sat down and gave some chest rubs, but her recall was still relatively weak. Finally we took her back outside of the fence, and in addition to the chest rubs and butt scratches, every time she came to us we would get up and move forward 30', giving her more to explore and it worked!
In the next 15 minutes we got about a dozen ready recalls out of the grass and in return she got to explore more. It proved the efficacy of the Premack principle (an opportunity to engage in more probable behaviors will reinforce less probable behaviors) but more importantly she was responding and giving some great behaviors.