I'm very paranoid about my quarantining. It is ideal to keep the new snake as far from your established ones as possible (ie in another room). It is better to at least put it on the other side of the room, rather in the same rack.

Definitely use different tools when caring for the new snake, and always deal with quarantines last.. after your established snakes.

After your handle the new snake, or touch anything in her cage, wash your hands for 30 seconds with antibacterial soap.

Oh, and update your sig.