Keeping a Puppy in the Yard?

Here are some great tips I found from the reddit dog training site:

For now, use a long leash or rope connected to a harness to prevent him from running off.

Ditch the food bowl and feed him every piece of kibble by hand. Take the food outside with you when he goes out. Every few seconds, call him back and give him a piece of food. He'll learn to stick close to you and check in with you automatically.
If you trick him by promising food and then not delivering, he will only be fooled a couple of times and then will trust you and obey you even less. Do the opposite--don't promise him anything, just make food appear by surprise.
After you get good at keeping his attention, so he never runs off and never hits the end of the rope, you can think about taking him outside off-leash again. But as long as he's reaching the end of the rope and being physically restrained, you need to keep using it to keep him safe on your property.