Having an assistant who is comfortable and knowledgeable with snakes is invaluable. It frees you up to actually take the shots yourself.

Having a proper setup is also good. Proper backgrounds, lighting, camera settings, etc. allow you to snap the pictures very quickly.

Knowing your snake helps as well. I find that a lot of snakes, when bugged and woken up, tend to be go-go-go for a little bit but many settle down well after a little handling. There are always exceptions, of course. So plopping them down right away for a photoshoot may not be the best method.

And the ultimate key... have patience. I haven't done much at all with my snakes but when it comes to my geckos I take a hundred pics to get a dozen good, useable ones. It's just how it goes.