I use long lines. I use 50 ft lines so there's little if any tension.
I take my kids on hikes through the woods -- with all the critters and scents that woods entail -- and I let them wander away from me and have a good time. Then I call them back to me, reward them with high value treats, and send them off again.
We do this over and over, til the kids realize that Come just means "check in" not "game over."
Come is THE most important skill my kids know, followed closely by "Wait" (because a dog that won't come often will just stop and wait for you to catch up).
Once I've done this over and over and over and over and over and over and over (and I'm also training in closed in areas like baseball fields as Ruth outlines), then I'll try offleash recalls in really distracting places like the woods. But I don't do that until my kids are out of their adolescent years.
98% trustworthy is a dog that can be lost, hit by a car, or killed by a mountain lion because he strayed too far away. Until you're positive he'll come back 100% of the time, he needs to be on a leash or a longline. Some dogs never graduate off the leash. It's ok. They're just lively, energetic curious dogs. When they're 10 or 12, they usually settle down and become reliable -- maybe