How can you put down a dog with out going to the vet and not make it suffer anymore?

If you truly love your dog, you will be responsible and take the dog to a vet, where they will administer the proper way of euthanizing it. If you can't ( or won't) do that, then PLEASE, do not EVER  own another dog again.  All animals have the right to be taken care of properly.  And the proper way is to take it to a qualified vet.

You can't.... and they don't 'suffer'....  the way people used to do it was to shoot the animal in the head.... can you look at your pet and do that?  Would that be the last memory you'd have of a pet or animal that you've cared for?  The injection to put an animal 'to sleep' is literally that is does go to sleep before the secondary medication stops the heart.  Wherever did you get the erroneous idea that using a vet would cause it to 'suffer'?  NOTHING could be further from the truth.... some pets are just afraid of needles period but most who are that sick, don't care.... You CAN find a vet to visit your home to administer euthanasia if that is your choice and, frankly, is the best choice.