h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Just my personal thoughts on regulators:

Look for magazine reviews of regulators, specifically the ease of breathing at depth and inclination to free flow. I and many other UK divers swear by Apeks regs, which are good enough for the Royal Navy, but there are other makes out there which are just as good.

Apeks also make a handy little gadget called a freeflow control device (FCD), a metal tube about an inch long with a sliding plastic collar around it. It sits between the end of the LP hose and the second stage, you slide the collar towards the reg, the default position, and air flows. If it freeflows, you slide the collar back along the tube and the airflow stops, and you switch to your octopus/pony tank/buddy. When the reg calms down, slide it back and carry on.

I cut the cable tie off the reg that holds the mouthpiece to the main body of the reg, tie a knot in each end of a length of shock cord and put in on the mouthpiece and then re-cable tie it all back together such that the shock cord becomes a neck-loop held onto the mouthpiece by the cable tie, with the knots to stop the shock cord slipping out from under the cable tie under strain. Keeps it round your neck if you drop it, but easy to slip over your head and pass across if you have to.

I also much prefer DIN fittings to A-clamps (DIN's screw into the tank valve for the uninitiated, which is far more secure than A-clamp). They are more secure, and can also take higher pressures if required and if the rest of your kit is also capable. There are different depths of screw thread for different pressures, to prevent you from plumbing high pressure air into kit that isn't designed for it, so make sure that you get it all rated to the same pressure.

Dive safe