D Loves Loves Loves playing fetch. So I take a small stick with me on walks, and I toss it for him when I need to get his attention. That keeps us moving in the right direction, as does chicken (chicken is his favorite food- he will do almost anything for chicken).
The other thing I do is carry him to a field about 2 blocks from the house, and THEN put him down and let him run around. It is fenced in, and there are no dogs, so I feel secure there. We take a long leash, and he climbs a few feet up the trees, we run around on the grass, and we play.