Teaching a dog tricks is a good way stimulate him and direct his energy in a positive direction. In addition, spending time with your dog strengthens the human-animal bond. Teaching a dog to untie your shoes is a fun way to get started. Choose a quiet place with no distractions so your dog's attention is fully directed upon you, and practice before mealtime so the dog is hungry and motivated to earn treats. Use soft treats so your dog won't be distracted by trying to pick up crumbs.
Dangle the shoelace in front of the dog to build his interest. Praise and treat him the instant he touches it with his nose or takes it in his mouth. Reinforce his action several times, five or six times every day, until he touches or takes the lace as soon as you show it to him.
Dangle the lace in front of your dog and say "take!" Praise him and say "release" the instant he takes it his mouth; treat him when he releases the lace. Increase the time he must hold the shoelace in his mouth before you give the "release" command, and do not reward him for letting go unless you say "release." Practice until he understands he must hold the shoelace until you tell him to release.
Tell your dog to take the shoelace, then give a slight tug. He should hold on, since he's waiting for the release command. Instead, say, "untie" and wait for him to tug back, which is a natural response when a dog has something in his mouth and you pull it. Praise him the instant he pulls, but don't give him a treat if he lets go of the shoelace before you give the "release" command. Practice until he tugs on the shoelace until you give the "release" command.
Gradually stop using the "take" command; instead, when you dangle the shoelace, say, "untie!" Practice until he takes the shoelace and pulls it when you say "untie!"
Tie the lace into a knot, as in a tied shoe, and practice the "untie" command until your dog pulls the knot loose. Treat him only when he pulls hard enough to untie the shoe. Give lots of praise and treats when he achieves this goal. Practice until he unties the shoelace confidently on command.
Insert the loose shoelace into your shoe and issue the "untie" command. If he's not sure what you want, break it down: practice "take" on the shoelace until your dog understands, then "release," and so on, until he will untie the shoe on command. Teaching the actual untying of the shoelace in the shoe should not take as long as teaching the original steps, since your dog is familiar with the commands.