Nearly titled this "Shooting Snakes" but thought that might mislead some. I don't kill snakes anymore, even the poisonous ones. I'm afraid with the loss of habitat and the senseless killing is cutting into the populations of some of these interesting reptiles.
I try to "shoot" my snake photos in as natural a pose as possible. Sure, the classic photos of a coiled killer serpent, ready to strike if an innocent person twitches is a big seller. But I try to put as little stress on my wild subjects (birds, mammals, insects, and reptiles) as possible.
As much as I like snakes I do take some reasonable precautions. Number one, I don't get too close. This is for my safety as well as the snake's. I recommend a moderate to long telephoto lens. I used to shoot snakes with a Sigma 105mm f2.8 macro. Great optic and kept me at a safe distance. Now I use a Canon 70-200mm f2.8, usually with a Kenko 1.4x teleconverter. Much better in low light, very sharp and...gives me even more distance from the subject.
Another good idea is to not only move slowly and smoothly but to ensure you leave the snake an escape route if he decides to take off, photo or not. Unless cornered the snakes on this continent will flee if given a choice. They don't want you, you're too big for them to swallow.
Best time to look for snakes is during the early or late part of the day. They usually stay in shady places during the heat of the day. This is ideal, photographically, since the best light to shoot by is also early and late in the day.
When you're doing close-up photography depth of field is hard to maintain. This becomes very apparent when you're photographing a subject that is a foot and a half to three or four feet long. As with all critters, make sure the eyes are in focus. They're the most important feature in the photo.
If possible get some close up shots and some showing the snake in its environment