A lot of my open water dives are with one dive buddy who owns his boat, and it's often just the two of us out in the Gulf. We came up with a pre dive checklist to insure we are ready to backroll off the side. We go down this list once we've strapped on our tanks and have done everything but don gloves and masks. You can laminate it and keep it in a pocket or somewhere else that's handy.
1. Dive flag.
2. Dive plan.
3. Gas on.
4. Check all regulators and submersible pressure gauges.
5. Inflation as required. (Flotation, drysuit)
6. Computers on and set.
7. Lights check.
8. Special equipment (as required). (Cameras, spearguns, tie-in line, etc.)
9. Weight belt on.
10. Knife on.
11. Gloves on.
12. Fins on.
13. Mask on.
Safe divin' to ya,