my DW works with a foster group. we have one in the house right now.
they take the application for the dog you are interested in (most around here do it that way)
check 3 references, call your vet to make sure you are current and a responsible pet owner-.
also they do a home visit with the dog to make sure its a good fit for both.
they usually take 3 days to complete the process and get the dogs to their forever home.
I really have enjoyed the fosters, we take them camping and I will take them to work.
I wish you well in your search!