Well, first, it depends on the snake. I've only got two here that are at all aggressive. And they are wee little things. So honestly I don't mind getting bitten that much. With an aggressive/defensive snake, (they aren't ever aggressive actually, they are scared. They are acting defensively, because I am big, and there is a natural instinct that hasn't broken yet that is telling them, "Don't get eaten!"), you want to try to pick them up from the side or underneath, not from over the top as this represents a more aggressive posture. Try to avoid the head, and avoid any sudden movements, as these actions are more likely to invoke a defensive response from the snake. Let the snake crawl over you, and your hands as compared to you moving it. The goal is to get the snake to realize you are not a predator, and this is truly a learned behavior. Some learn it very quickly, and some hold onto for a while.
For the more tame animals, just be kind and gentle. Really, that's it. Don't force the snake anywhere, you can move them in any direction you want. I give all my animals a thorough check up every so often, including mouth and teeth, and yes, I open their mouths. With a tame animal, honestly, it is just common sense. Don't poke it in they eye. Don't squeeze it hard. Don't drop it, make sure to support the snake if it wants to cruise around and explore.
