One thing no one else mentions - be sure to pop the handle adaptors (the ball heads) to your strobe heads out of the tops of the handles in the tray, and DUMP THE WATER out of the handles. They do tend to hold water, which means saltwater in the ocean of course. I keep meaning to drill a small drainage hole near the bottom of my handles but haven't done it yet.
Other than all the above advice, which I agree with (the biggest key being WORK THE CONTROLS in freshwater else the salt stays trapped), my only other 'care and feeding' tip would be that I like to release the rear main seal buckles slowly, so that they stay 'hooked' with pressure released until all three are open, then I swing the catch out of the bail. When sealing, I hook all three passively before snapping down the first one - otherwise the rear plate wants to 'pull' a bit to one side and I think this could either result in displacing an o-ring or just misaligning the camera slightly to the controls. Also, depending on your camera, if any of the controls have the sliding shafts, make sure they're slid and/or rotated 'out of the way' of the camera when inserting it...you'll save yourself a lot of hassles later on. Especially true of the lens release control - if that's pressing in on your lens release button, then in some cases the camera won't "see" the lens as connected and show you aperture data even if the lens bayonet mount is turned (this happens on my Olympus).
Last tip, is PRACTICE assembly and disassembly with any and all lenses and ports you intend to use. Not all ports are the same. Some super wide lenses (like my Oly 7-14) must actually be put on the camera AFTER the camera is in the housing and the rear main seal in place, and the lens port then cautiously slide over the lens from the front. Learn where each of your lenses likes to have the zoom gear and coupling located on them, as minor differences in sliding these front to back can make or break a contact to the zoom controls. This will save you a lot of frustration later on, trying to do it the first time on a potentially rocking liveaboard in tight quarters. 