Question about training a new command to my mutt?

Use different commands. I use close if it doesn't matter where the dog is at. He can be on either side, ahead or behind. He just has to be within 3 feet of me. For heel the dog is on the left side, neck right at my left knee, within 6 inches, and walking with his head up and watching. the dog is also expected to sit at heel when I stop. I use a combination of treats, praise, toys play and corrections. Mixing it up keeps your dog excited and wanting more.