To teach a dog to leave it on walks, start by introducing the cue in a controlled environment, such as at home, and gradually increase distractions. Start with a tasty treat under the toe of your shoe, let your dog sniff, lick and paw the toe of your shoe, and patiently wait until they get bored and give up. The moment they turn away from your shoe, mark it with a word or clicker and reward your dog with a treat from your open palm. Next, add your cue, make eye contact and say “Leave it!” firmly when your dog first notices the treat under your toe, and reward them with a tasty treat from your hand when they turn away.
As your dog becomes more proficient, practice the "leave it" cue in different locations, such as on walks, and in the presence of various distractions, like other dogs and birds. Start using your “leave it” on regular walks when they’re on their lead, trying it first in quieter areas, and asking your dog to “leave it” when you see anything interesting on the ground or approaching you. The key is to ask your dog to “leave it” when they first notice and begin moving towards a target. If your dog fails to respond, calmly put them on their lead and stand still, holding them close to you for 30 seconds to 1 minute.
In advanced training, try your leave it cue in a quiet area when they’re not on their lead, and you can try throwing a toy or simply ask your dog to leave alone things like other dogs and birds. Remember to say your cue when your dog first goes for something, not when they’re in the middle of a chase, and to give them a short spell on their lead if they fail to respond. Mastering the leave it command will help keep your dog safe and make your walks more relaxing and enjoyable.