Has anyone found a way to run a wait list successfully?

When I am contacted by a potential client and don't have spaces, I am often asked if that family can be added to my wait list.

I have swung from having one and not having one because as a low turnover day home, I never seem to have a space when those on the wait list require one. Most parents on a wait list want a space for a specific month. When I have a space I always find that it is after those on the wait list need care, or it's months before a wait list family need care and they are loathe to pay for a space to hold it or with just 4 weeks notice required from a departing client, those whose start dates fit with the vacancy have often contracted for elsewhere.

The only time I seem to get it right is when I know a child is aging out for Grade Primary and so of course can contract many months in advance of that child departing.

Do you have a wait list?
Do you find it useful when you have a space?
How do you manage it?

Thanks