I let Max and Teddy sniff, but if they take too much interest in an area, they often are up to something naughty. When they plant their noses and start spinning in a circle, they often are digging up something like a dead bug, or something dropped on the ground that could be hazardous (chocolate, bones).
When I want them to move along, I say "Let's go" and I move their leashes such that they brush their backs or give a slight tug. They know to move along because if they don't, they will get helicoptered away from the spot (the benefit of being in a harness).
