There is no sense in taking a chance on a litter if the owners are only guessing what they may or may not produce. Ask questions . Ask about their failures, too. No one likes talking about them, but if a breeder is experienced there is always a hitch or two somewhere. Most important is to see as many adults of the type you need as possible before you see a litter .
All pups are cute and many are good sales people.
Know what you want before getting there and don't let someone talk you into taking a pup that doesn't quite fit your bill. Don't expect a total guarantee that the pup will work exactly how you want from any breeder. How the pup will work depends on you or your trainer. Even the best worker can be messed up by bad training. Do expect good advice, help and support.