With any new snake we get we first focus on settling the snake in, feeding it, changing it's water, doing cage maintenance, weighing the snake and so forth. We don't even bother with handling at first other than for the above mentioned things and just act very calm and matter of fact around the snake. This I think allows them to begin to recognize us as non-threatening and a scent/heat signature that they can begin to recognize in a very basic manner.

Once they've been here a few weeks and are eating and settling in well, we just reach in, gently touch the snake down the lower third of it's body to let it know it's coming out of it's enclosure (we do this every single time a snake is to be taken out), then lift the snake out and sit quietly with it. After enough repitition of this most of them begin to recognize that body stroke = handling time and it's no big deal or anything to get defensive about.