Great thread, with tons of good tips. So, a couple that I've learned along the way:
When deploying an SMB, make sure it's hooked to the line, not to the bolt snap on the handle attached to you...
With all of the "dry" snorkels out there, this is one I've had to use frequently. Often the "one-way" calve at the bottom of the snorkel sticks. Here is where a blast of water really helps, as it can reset that valve.
When checking reg function prior to jumping in, if you watch the SPG and the needle drops and returns, then your tank is just barely on, and probably won't be open enough once you get to depth. (frequently happens when you just crack the valve to check pressure, but forget to open it the rest of the way.)
The loop bungies with a little ball on them (often sold as tent bungies) are great for snugging stuff up and streamlining your gear. Plus they're cheap, so you can replace them before they get old without being out a lot of money.
Listen to the DM brief. They dive the boat/site regularly, and know what to expect. Trust me when I say you probably aren't going to come up with a better way to get into the boat. Maybe a more entertaining one...
Mike