Bogertophis is dead on, but I will add that you want to handle the new snake last, feed last, clean up after last, etc.
They should be as far apart as possible if in the same room and as mentioned, use different tools - hooks, tongs, bowls, etc.
I also recommend when in quarantine to use paper substrate and white water bowls. This makes it more likely to see things like mites, if present, and keeps it easier to clean and keep clean.
Good luck and keep us posted.