Apart from keeping a bitch myself, my own enquiries and being being referred some potential owners via friends in the gundog world. I now have a waiting list of 9 for a litter that was only mated on Sunday. They have all been spoken to and vetted at length by myself, have all details and in most cases have visited us before mating. There is a mixture of people who only want girls, only want boys or don't mind. This breed can have between 6 to 10 pups, and the litter is also potentially going to be looked at by Hounds For Heroes for a dog too. An awful lot can happen between now and the end of July if all being well this litter will be ready to leave, but I'm very pleased so far with who is on the waiting list. The problem is I'm still getting good enquiries and the litter isn't on the ground yet.

So how many do you take on a vetted waiting list before closing it?

Thank you

I tend to take 3 for each sex, and then tell any new people that there would have to be more than 4 of the sex wanted, so their choice, to try to get higher on another breeders list first. 

The average litter size in my expereince of my breed is just about 6.  I have most often had 4 to 7.

No, I kept the list open unless numbers got ridiculous.  You never know, what if you get a big litter all the same sex?  I had a litter of 11 once(in my previous breed) and the majority of the litter was boys.  If I'd have closed the list at 4 or 5 for each, I'd of had a few boys to sell. 
What I tell people is, they are on my list and whilst I hope to have a pup available for them, I can't say for sure till they are all here safe and sound.  In the meantime they are welcome to get added to any other breeders waiting list but I so ask for a call if they've gotten a pup elsewhere so someone else can take their place.  If, when the pups are born, there are not enough pups, then I let them know straight away.  I think that's OK.

I tell people that I note that they are interested in a puppy and then check them out.

I then tell them if I have anything I think is suitable for them I will offer it to them.

Thank you so much for replying so quickly, I will keep the list open then, as you say I could get a whole litter of one sex. I'm keeping very much an open communication with them all and it also means that I've got plenty of time to build up as good a picture as I can of each family.

I would keep it open as well, and keep communication open.  A lot can happen between now and then.  I had 6 'definites' before mating, and in the end only one of them had a pup from me.  Everyone backed out for different reasons, plus I only had 2 bitches (2 wanted bitches) and I ended up keeping both - had 5 boys.  One of my 'bitch' buyers did decide after a time that they would have a boy (for which I was thrilled as they have a girl from my last litter and it's worked out perfectly all round), so they were the only ones on the original list that ended up having a pup.

Times are tough, circumstances can change quickly, and if there's a few litters on the ground at once, something as simple as colour (for a pet buyer - and even sometimes for a show buyer) can sway someone to a different litter even if they are 'definitely committed' to yours...

Thank you :) at least I know what colour they are all going to be, there is only one option from a yellow/yellow mating lol. Think it would make life much harder if there was a big choice of colours too!

I don't keep a waiting list, when people contact me I ask them to keep an eye on my website and once the litter has been born to contact me again.

Keep the list open but help them look for a puppy if you aren't able to help them. At least then you can point them onto a quality litter instead of them going down the pet shop road.

I ask them to call back nearer the time. I have learnt that people change their minds so quickley, or they want a puppy NOW. After 2 litters with waiting lists where NONE of the people on the list had a puppy, I gave up.

what I do with my list is at each stage (mating, confirmation of pregnancy, birth), I contact them to confirm their continued interest (those who don't reply are dropped, some even reply to the negative which is polite).

As you say people drop out and new ones are added.