The trick is for the first several months to guarantee they don't get a chance. Like smarsden said, every hour on the hour and after eating, drinking, or playing. Also, if you can't have full attention on the pup, he needs to be confined to avoid an accident. Winston goes out in the morning first thing, comes in, has breakfast, chases a ball around for about 10 minutes and then back out we go. Once he eliminates in the yard, we go for a walk as a reward, get home, wait in the yard again at which point he will usually go, and back in the house. At this point, I have to get breakfast going for my little humans who are just now waking up, since the husband isn't likely to actually get out of bed for another half hour or so. Rather than popping him back in the crate for this, I secure his leash to the cabinet, he can stay close, I can keep an eye on him, and everyone is happy. After breakfast is cooked for kids, Winston goes back outside to go potty, comes in for a cuddle, and then goes to his crate with a stuffed Kong while I get the kids dressed and pack a lunch for the husband. About an hour later, back outside, come in for a game of tug of war and some fetch, outside again, back in the crate. Another hour, back outside, 20 minutes of training exercises, back in the crate. He's out the entire time the kids are napping because I can focus entirely on him, after nap we all go for a walk unless the weather is too unpleasant for the kids, in which case Winston and I will go alone when the husband gets home from work.
He never goes out and straight back to the crate, but he is always in the crate at some point between trips out. Most pups won't mess where they sleep, so it's an ideal safeguard when you can't be right there. With two toddlers who also require my attention, I can't be 100% focused on Winston at all times, and when I can't, I know he is safe and occupied happily chewing his Kong toys to pieces and resting.
Andrea- Mommy to Winston, blenheim boy born 12/10/2011, and two human children, George 6/11/09 and Lela 1/25/11