Using a leash is a necessary part of having a dog; many places require you to use a leash if you take your dog out. However, some dogs, such as some rescues, are not used to being leashed and sometimes it can be a tough task to get them used to being on a leash. Usually it is dogs that have previously had a bad experience, or with being trapped or caged for long periods of time, that have the worst problems with leash training. Most dogs usually do not have many issues with the leash; they are a fairly adaptable species.
You have to ensure that your dog doesn’t associate negative things with the leash. Never put your dog on a leash and leave it tied up as it can get it wrapped around something and choke them. Proper tie-ins that specifically are designed to prevent a dog from choking themselves are fine, but leashes are not designed for this. Only use it for walking, being in public and maintaining control of your dog when outside the home. Never use your leash as punishment, as the dog will develop a fear of the leash due to the negative association in their mind of its use.
It’s much easier to train a puppy, since an older dog may already have had negative experiences with a leash. The best way, obviously, is to gradually introduce the leash to them:
First, leave the leash on the floor for them to smell and just getting use to it being around. Try to praise them every time they walk close to it and look at it or smell it. After a couple days maybe leave a few treats on the leash to tempt them, then make sure you praise and give treats when they come to it again. You are trying to program your dog to associate the leash with good things, like treats and petting.
Then attach the leash to the dog via collar, and just let the dog walk around with it on inside the house. Do make sure you supervise this; you don’t want it getting caught on something and panicking your dog. Again, use positive reinforcement like treats to help them associate the leash with good things. When your dog is comfortable with this, it is time to move onto the next step.
Leaving the leash on and having a pocket full of treats, lead your dog out to the yard and walk them around a bit, seeing how they react. They may not like being on a leash in previously free territory, so if they seem uncomfortable, don’t stay long. Take them for a very short walk in a quiet path near your house. The treats and praise are essential here because you are continuing the positive reinforcement and helping your dog to associate the leash with good things.
After this walk, lead your dog back into the house, and before you take the leash off praise them and give a few more treats. Repeat the process of walking them around the yard and short walks with the positive reinforcement at least once a day until they become comfortable with the leash. This should help your dog greatly instead of trying to force them on the leash. It yields much faster and more positive results.