Well, what naming convention does your breeder use? In my experience, each litter is assigned either a theme (more inclined in show dogs) or a letter (working dogs.)
If I don't especially like the formal name or variations of it, I tend to work on geography pertinent to the dog. If I get to choose the formal name and it needs to start with a specific letter, I pull out the dictionary and build a list from there. Then I use elimination.