I brought my first sheep direct from the breeder, both times they were pedigree sheep, breeder advertised in freeads. Since then I've brought sheep when something cought my eye on facebook, freeads etc. Most of the poultry, goats, pigs I've got the same way, been browsing and spotted something that took my eye.
I either tend to look around for a bargain, or I see something I like the look of, at the right price.