we have a 12 month old shih-tzu bitch
we would like to breed one litter but need a stud
can any one give us any information.

Hi, 12 months is too young for any breed of dog to be bred. Please wait at least until her third season, and pref til 2 years old. Have her examined by a vet to make sure she is constructed properly. In the meantime, find out as much as you can about the breed by visiting shows, surfing breeders web sites, other breeders to see if your dog resembles them. Just because a bitch has a pedigree does not necessarily mean that she is of a suitable standard to breed from.
It is also very expensive, risky for the bitch, extremely time consuming and worrying and very rarely profit making, despite what most people think. Selling the puppies will not be easy, and most owners of quality stud dogs would not want to use their dog on an inferior bitch. Please dont take offence, I am sure you love your dog greatly, and to you is the most beautiful dog that ever breathed, but is she a good example of her breed? Would you recognise one that is, from one that isn't? Please think twice.
Just because you might like to keep a puppy is no reason to bring a litter full into the world unless you are reasonably sure they will not produce hereditary defects, litigation is rife these days and courts very rarely find in the breeders' favour. Do you know what hereditary diseases affect this breed? Has she been screened for them? If you would like another dog, it would be far less risky for your bitch, and much less expensive for you to buy a well bred well reared puppy from a reputable breeder, if you post again, looking for one, I'm sure you'll be directed to a cracking litter very quickly.