I've lost count of how many "mean" "aggressive" snakes I've taken in over the years that owners (or in one case, a PET STORE!) had given up on, that never bit me...
The Golden Rule applies heavily to snakes: Just treat them as you'd want to be treated if you were in their place.
And remember they don't rely much on vision to identify things, & have very little hearing, so your cues are pretty much limited to scent, touch, & body heat for those with heat-sensing pits.
"Touch" is the most important one. Try hard not to startle them & always do your best to identify yourself when you approach & interact with them- they'll show their appreciation by being calmer.