Off the top of my head:
Disconnect the separator so that it can't closes, basically by removing the negative for the switch (a small ground wire). If you want to be extra careful you can pull one of the major + wires and wrap the end in electrical tape to ensure it doesn't contact anything (one wrap is enough as you're not driving around, it won't be rubbing on anything etc.)
Second, turn everything off. Pull minor fuses. This isn't absolutely necessary in my opinion, but helps protect the equipment. More importantly it will prevent sparks when reattaching the negative later.
Disconnect the negative cable from the battery. You can check if you have a draw by tapping or brushing and looking for a spark. Careful, as my Xantrex KEPT turning itself on... about 3 seconds after having no draw, I'd get a draw because the Xantrex was back on.
Once the negative is disconnected from the battery, the positive is essentially dead, so you can hit the frame with your wrench (or knuckles) when disconnecting. Of course be careful not to bridge the terminals on the actual battery.
Last be careful when moving the battery out, especially if frame clearance is an issue...
Reconnect in reverse order, positive first, then negative.
Hope this helps, I'm sure someone will clear up any omissions or mistakes, hopefully before you turn something into slag.