I adopted Cuddles from a kid who didn't want her anymore.
I learned everything I could about all the health problems my pigs have had (lethal white, ovarian cysts, bladder sludge, diabetes) so that I could give good advice to people dealing with the same problems in their pigs.
I threw in a lot of anti-breeding facts on the wikipedia page for
Guinea pig breed - Wikipedia, the free encyclopedia such as skinny pigs' higher incidence of melanoma, satin pigs' higher incidence of osteodystrophy, and roan/dalmatian leading to lethal pigs.
I post anti-breeding stuff here of course!
I promote better guinea pig care, and C&C cages, to everyone I can, even if they don't have guinea pigs. I also encourage people with cats and dogs to switch to healthier high-end foods for them, such as Innova and Natural Balance.
Anyone I know who has bunnies, hamsters, gerbils, etc., I direct to appropriate sites such as
House Rabbit Society Rabbit Care Guide.
I frequently use the words "adopt" and "petfinder" in casual conversation.
I also tell people of the dangers of pet stores, and stress that all animals are available in rescues, and pet stores are full of sick and mistreated animals.