
Difficult one this as apart from the dogs I have used abroad where I got to know the stud owners over the Internet, after having sought information on their dogs and asked the possibility of using them, I have always known the stud dogs and their owners (as we all meet sooner or later during the year at shows), so it's simply a case of asking once you know what you need to know (studied their offspring, siblings parents, health results etc).
I assume you will already know the dogs by sight, and had a god opportunity to meet the ones your considering, if not take the trouble to at a show or event. This way you don't need to say anything to them until your sure.
If that can't be arranged you will have to approach the owners and say your considering several dogs and would like to meet them if your bitch would be acceptable to them, and offer to give/send all her details to them.
Well they will want a pedigree to see if there is anything they would want to be aware of and whether they think it looks good on paper (meaning likely to produce the quality wanted).
I would imagine the stud dog owner is likely to be aware or be able check the bitches track record in the show ring/working arena.
It would probably be a good idea to mention which shows/working events she will be at over the next few months so they can take the time to look at her more than in passing and hopefully get to meet her to judge her temperament.
Ask for the stud terms in writing in advance, assuming the stud owner is experienced themselves. If they are novice owners of a good male they may need for the mating the services of someone experienced, I have used males owned by Novice stud handlers so handled the practical side myself, and at other times have been able to leave all in the stud owners hands.
Again if the stud owner is not the dogs breeder or very knowledgeable themselves, then the advisability of the pedigree producing good results/minimum chance of problems is best discussed with the dogs breeder/owners of his parents.