BTW, I don't know if I can unconditionally agree with some of these:
Only 1-2 litters per year
Specalizing in only 1-2 breeds
Vet checked and wormed and first shots
Health guarantee
I don't know of many reputable breeders who schedule their litters to 1-2 per year. Some only breed when they know they're going to be able to use some fantastic dogs, which is sometimes 1 litter every few years. Others will find some *superior* dogs and do a couple litters at a time. It really fluctuates with the quality of dogs they find.

I also know of some AMAZING breeders who specialize in more than 1-2 breeds. It takes time to familiarize with a breed, but it's not unheard of to have a reputable breeder in more than 2 breeds.

Vet checked, wormed, and first shots are as basic as food and water. Even BYB's and PM's usually do this. I wouldn't even keep this in mind while looking for a breeder.

Health guarantee: READ IT. Please please please read whatever health guarantee a breeder gives to you. Some only guarantee the first year. Yeah, okay, but a lot of genetic diseases crop up after the 1st year. What then?! Read the health guarantee, consider the genetic diseases prevalent in a breed, and weigh the risk. Health guarantees are very tricky things because it's such a multi-faceted issue, so please read the guarantee carefully.