What breed do you have? What experience have you in that or any other breed? What success have your dogs had in either a working or show environment, to ensure that their offspring would be wanted by puppy buyers?
Do you know what is behind your bitches bloodlines, and what other bloodlines are compatible with hers?
What health problems are your breed beset by and has your bitch been tested for them? Has she a suitable temperament and is she a good specimen of her breed?
Do you have the time, facilities and money to correctly breed and rear a litter, bearing in mind that it could cost you a lot of money should the bitch require a c-section and you might end up having to hand rear the whole litter, or even lose the bitch and puppies.
Have you the space to keep all the puppies if for any reason you are unable to sell them? Would you be able to take back all the puppies should the new owners be unable to keep them? Would you be prepared to vet all the new owners and ask them all the right questions?
Here are a couple of sites that might be of help.
http://www.dogstuff.info/to_breed_or_not.html
http://www.spinillons.com/Thingstoread.html
As you say dog breeding is not something that should be taken lightly. I suggest you look back through some of the questions on this forum and you will get an idea of some of the many problems involved with dog breeding and health.