This site primarily focuses on all things cat, but since it’s not uncommon to have both cats and dogs in the same household, I have a couple of articles relating to dogs, like this one.

To start with, the weight and width of the collar should be proportional to your dog’s size. You also want to make sure the dog collar fits you and your dog’s day to day needs. Small dogs will have much different needs than large dogs. If you have a large dog that tends to lunge when he gets excited you’ll need to take this into consideration when looking at collars.