[QuickSilver]

I think it depends on the dog. Some dogs are never safe off lead.

My understanding is that you should always reward when they return, be it a treat, a pat, praise, something they really like. A lot of people also say that you should never call them for something unpleasant, like a bath; just go get them, so that returning to you is 100% positive.

You can start in your house so you don't have trouble with him running off. Let him see that you have a treat and use the whistle (or "Come"). Reward him every time until you can try it outside, in your yard if possible. Then go somewhere more challenging like a baseball field.

Thor is naturally somewhat timid, so I found it pretty easy to train him. Several times per week, I walk around a park with him off lead. For months and months, I gave him a small treat every time he returned to me, even if I didn't call him, to give him the idea that checking in with me was fun. When I formally called him, I gave him two treats.

Now I only give him a treat sporadically when he returns without being called (though I always praise him), but I still give him a treat almost every time he returns when called.

It's important that this be a really positive experience for your dog beause obviously it's a command you can't immediately enforce. Never scold your dog for returning, even if he is slow, because that will just teach him that he shouldn't come back. Once he really gets it, failing to return to you on command should be regarded as a major infraction that results in him being physically brought back to the spot where you called him from.