Breedings: All of my male dogs go up for stud after reaching level 30. I check on the females and I only reject requests if your female has been bred more than 2 times already.
Litter bids: Generally first come, first serve. Minimum price is always $0, but if I'm not happy with your bid i won't accept it. Only progenitor achievement pups will be sold for free.
(Under construction, more stuff later)