just go out and look for spots. Try to find grassland areas with a lot of rodent holes. Keep your eyes open for boards,tins, and other assorted junk because snakes like to hide under it. I know there's a lot of good spots in Carlsbad but I don't live there so I'm not familiar with them. I have found my best spots by hopping on my bike and exploring areas where there could be snakes. If you want more advice try the field collecting forum.