At foundation classes it was lead in right hand dog on left. Next class said that was b******s and it was handler's preference and best control, and next class made us practice both. My groomer walked Sir home yesterday and said, you know he is odd, on the left he walks to heel perfectly with a loose lead, and on the right he pulls like a steam train. I agreed that he is odd, and said I suspect its about where the most interesting sniffs are. I try to practice heel on both, but believe me, we are a million miles away from whatever is required by competitive obedience! We always get the correct side in agility though!