When the wind is amazing and the sun is shining, the last thing you want is gear failure to totally ruin a great kiteboarding session! Am I saying you should inspect everything each time you set up for a ride? Well, yes.
Kites: Leaking
The most common malfunction is leaking. If you leave your kite in your car during hot days, expect this to happen sooner than later, and go ahead and buy some Aquaseal for re-gluing all your valves. Otherwise, make sure the valves are fully closed and locked down (Velcro, etc.), and if your kite has a "click-to-close" system between the leading edge and the struts, make sure they are closed before launching your kite.
If your kite begins to lose air while you are riding, hopefully you will have enough air left in the other bladders to make it back to the beach. (Note: if you cannot make it back to the beach, you will need to do a self-rescue.)
Kites: Bridal lines
The areas to look out for are where the pulleys (or rings - Epic kites) rub against the lines. Make sure they are working properly by moving them back and forth, using water if necessary to clean out sand and dirt in the pulleys. Check the bridal lines for wear, looking for any fraying of lines.
Broken bridal line
Boards: Loose screws
To be clear, I am NOT talking about the kiters, although we get accused of this quite often. The loose screws I'm referring to are the ones holding down your bindings or footstraps. Eventually these screws will begin to loosen up and you don't want to be 1 mile out in great wind and realize your bindings are falling off of you board. Almost all of them tighten down with a basic Phillips head screw driver, so keep an extra one with your gear, and tighten them regularly.
Kiss The Sky Kiteboarding