Get an anvil and a name tag (creative mode). Click on the anvil, then put your name tag in the empty slot. Next, type in your dog's name. Then take your name tag out of the slot, escape the anvil, then put your name tag on your dog. read more
Next, type in your dog's name. Then take your name tag out of the slot, escape the anvil, then put your name tag on your dog. A bar with your dog's name should appear above your dog. read more
Enter a name for your name tag. You'll do this in the "Name" field at the top of the anvil's window. On console editions, you'll first have to select the "Name" field and press A or X'. read more