When it comes to puppy collars, a cheap nylon collar that is long enough to leave space for your puppy to grow into is a great option. This should be done with the first couple of days of bringing him home. An adult dog collar is usually worn loose enough to be slipped over his head with little difficulty, but that is too loose for a puppy. It is not that difficult for a small leg to get caught in that space, as chances are he will paw at the new collar. The best fit should be enough to get a couple of fingers under the collar.
Puppies do not react well to new things, and they will express their displeasure by scratching and clawing at the collar to try and get it off. This should not be taken as a sign that the collar is itching, but rather that they find it uncomfortable and want it gone.
Whenever you take the puppy out to go potty, which will be often, use the collar and leash every time. This is a great way to get him used to the feel of it. A puppy is less annoyed by a leash than a collar, but when you attach it for the first time, let him drag it around a little (pay attention when he does). After a few moments, pick up the end and let him feel the difference. He may object at first by twitching and pawing at his neck. Puppies that are really resistant may even relieve themselves at this point. Once his resistance ends, you can move to the next step it stop for the moment.
Once he is done putting up a fight, you can try to coax him along by giving a few gentle tugs on the leash, accompanied by soothing words of encouragement. Pups that remain resistant can often be “bought" with some small moist treats. However long the training takes, make sure to always use positive tones and praise for appropriate behavior.
A couple of things to remember about puppy leashes and collars:
The chances of this happening are pretty slim, but there have been instances when puppies have choked after catching their collar on their crate. Manufactures who make crates recommend that you should NEVER put a puppy in his crate with a collar on.
You may find that your pup will mouth or chew his leash, particularly if he is a retrieving breed. This is something they usually outgrow. If this becomes a common issue that leads to a tug of war every time you use the leash, try spraying the end with something bitter (these sprays can be found in the pet shop), or attaching the leash in foil.
“Slip" or “choke" type collars are for training purposes only, and should never be left on when the leash is not being used.
Get in the habit of checking the fit of the puppy’s collar on a weekly basis, as they can imbed in the neck if they are too small.
Get ID tags made and attach them to the collar ASAP.