I want to make some money!

Breeding, and doing it right, is an expensive undertaking. By the time you've picked out a good bitch, waited for her to grow old enough (minimum age: two years before breeding), picked out the best dog to mate her with, gone through all the health checks she needs, ensured that the dog you want to use also passes the same health checks, you've invested a lot of time and effort. You still have to pay a stud fee (or give a puppy back), you have potential extra expenses during pregnancy, you have the time and expense of whelping (either you take time off from work or something goes wrong and you have to take her in to the vets).

You need to keep the puppies for a minimum of 8 weeks before sending them to their homes; you need to advertise and find good homes for the puppies, you need to make sure they have had their first vaccination before going. You may have possible vet bills if the puppies require extra attention. If some of the puppies die, or you have a smaller than usual litter, you may not get as much money from the sale of the puppies as you had thought. There are even potential problems later on with dissatisfied customers! You are better off consulting with a financial wizard about investing the money you would otherwise spend and lose on breeding!
Breeders frequently count themselves lucky if they break even.

My kids should see the wonders of birth and life!

What if the whelping goes wrong and dead puppies are born? What if the bitch dies? These are all very real risks that you are undertaking. Much better alternatives include videotapes that are available.
Or, you could contact your local shelter and see if there is a pregnant bitch about to whelp or a litter of puppies that need to be raised and socialized before being adopted out. This would allow you to find out just what this could entail, while helping the shelters rather than potentially contributing to the problem.

I want another dog just like mine!

If you want to breed your dog so as to get another dog like yours, think about this for a moment. No matter how special your dog is to you, a puppy out of it is not guaranteed to be just like or even similar to your dog -- half its genes will be from another dog! You will have to find another dog that also has the characteristics you want in your puppy; that dog will have to be un neutered; and the owner of that dog will have to be willing to breed her/his dog to yours. It is much easier, often less expensive, and certainly less time consuming to pick out an existing dog that you like from the shelter or another breeder. Best yet, go back to the same breeder of your dog, if possible, and pick another puppy out of similar lines.

Every bitch should have a litter!

This is flat out wrong. Bitches are not improved by having puppies. They may undergo temporary temperament changes, but once the puppies are gone, she'll be back to her old self. Nor is it somehow good for her physically. In fact, you will put her at risk of mammary cancer and pyometra. There is absolutely nothing wrong with spaying a bitch without her having a litter.

But my dog is registered!

Well, yes, but that doesn't mean a whole lot. A registered dog, be it KC etc., simply means that it's parents (and their parents) are also registered with the same registry. This confers no merit in of itself, it simply means that the dog's parentage is known. Most registries do not make any assertions of quality in the dogs they register (except for some limited breed-only registrations, but these are uncommon). They do not restrict the breeding of their dogs and hence there is no guarantee that a registered dog is a good specimen of its breed
So I should breed when...

The only reason you should be breeding is if you honestly feel that you are improving the breed by doing so. There are far too many dogs in this country to breed without good reason.