Does he have a watch me when not walking? If not teach that (there's lots of instructions online). Then start using it while walking around the house (boring, no temptation to sniff), then outside in the yard where the smells are familiar, then gradually in more and more exciting places. If he doesn't get it in a new place, back up a step, don't try to "force" him to be right in the harder environment.
Good luck! I taught the different positions by doing three-step pushups - down, sit, stand, and back down again. Then you eliminate sit in between, or just do sit-stand - mix it up.
Becca Shouse: Irena Farm, Semora, NC

Cord, Ted, Gus, Zhi, Maggie, Lynn, Lu, Min and Tully
Waiting: Bubo & Ben
"We didn't have a phone, and we couldn't call you!" Helen, AIDS orphan. Don't let them die of ignorance - WorldHelp.net
"I-Dog Biggest Loser" Official Cheerleader/Mascot

Start 09/15/08: 186.4 lbs Current 185.5 lbs