Just a few things I've managed to screw up in the past...
First of all, I wouldn't go
anywhere near my housing with a blowdryer. I usually try to load my camera in the room in the A/C pre-dive. You want dry air but not necessarily hot air. Especially with a metal housing. And be really, really diligent (
anal) about checking the back seal for any junk, hair etc before sealing it.
When you get on a boat, put it in the rinse tank and
watch it a few seconds to make sure the bubbles are all from the outside. Most photographers also get a little tense when they see your 7.6 lb. housing dropping down near/on their $1500 dome ports so be aware of that.
Then either leave it in there till you dive or take it out and put it covered in a shady spot. I've heard both ways, mine rides in the rinse tank and I've never had a problem.
On a boat always have the crew hand your camera down if possible. I have on occasion jumped with mine but it's always a tense moment. If you have a water alarm, turn on the housing before you leave the boat.
You do have some sort of good lanyard right? I have
this one, it clips to my upper d-ring so the camera is held high for shore entries yet easily deployable. I slipped a locking carabinier through the other end that fits conveniently in a hole in my housing handle.
I power up the camera on the boat and get it ready while descending, I've twice been able to film something interesting coming by to take a look at the
new guy under the boat. (Barracuda and free-swimming remora)
For shorediving, mine rode wrapped in a towel at my feet. During a week of filming on Bonaire I never had any fogging. And I don't use any sort of dessicant. It's been my observation that only people with poly/plastic housings need to worry about that, ymmv.
Everything CG posted. One bubble will ruin your whole day of shooting. (spoken from experience)
Generally stay in the wide angle range and get closer. Most people can't hold their housings steady enough when zoomed in on some object 20-30' away and it's nauseating to watch later.
You'll also be surprised how having the camera messes with your bouyancy. It's easy to crash into things while you're distracted during filming. They're really going to frown on that in Bonaire....
Other stupid things I've done:
Forgot to plug the camera in.
Forgot to remove/open the lenscap - twice.
Hit the nightshot switch during loading and later watched everything go bright white as soon as I tried filming. You can't turn it off electronically so that was a good dive but no video.
hth,