I asked the same question on another forum. Since, I live in the burbs, listening is crucial. Anyway, here is a simple rundown from a professional trainer.
"This is how I teach it, when you have taught the command and the dog understands the command, what I do is command, see if dog responds, no response, or just farting around, command-nick low setting-command. always repeat your command after nick it puts it together indogs mind. I think in your case with the city, I would do it with check cord also to start out. Don't use long cord 10 ft. max. You figure out how you want to have dog come to ya, most of the dogs I've done have been done with name-here. Put your cord in right hand, remote in left, when I teach here I use a stronger tug, so now it will be command-tugnick-command. Pet on it send on, walk around for little bit, repeat. You'll see after 7-10 times dog will start coming in with no tug, and posibly no collar, it is learning that nothing happens if I do this. And there will be times of "screw you" So collars on, repeat command-nick-command. So you gave dog chance, it thought it was ahead of you, you made the correction. I have put collar on early in the morn. worked dog in afetrnoon, turned it while I was petting it, dog didnot relize it was there. Excellent correction made. You got to give dog time to learn!! Patience is a virtue. If you don't have a collar there is place called collar clinic, its about the cheapest to get collar, or have one worked on. What they do is use the old casings of the transmitter, and reciever, shell out put in all new guts. Excellent price. My self if its that busy where your at, I would be careful about the area ans not let her off the cord, she'll use the bathroom. Use the shorter cord that way if she's running circles you can feed rope around you not get tied up!! Jonesy "
As to how soon, he never answered it. My guess is when teaching woah. Although some say not to use a collar until a year old and only for correction.