CRAP is a good quick reminder before every flight.
Here's a longer list when first starting your flying day.
If using FM and around other pilots, check frequencies before turning anything on. I have heard stories of planes crashed because someone turned on a radio while not even near the flight line. Also check every time you go up because someone else may have arrived and no one noticed.
If you are anywhere near an airport be extra cautious. I had a nitro truck go nuts and destroy itself into a tree at full speed because of interference near an airport.
Check the field or flying area, park etc. Check for obstructions, water, people, animals, traffic etc.
Check for damage while transporting
Charged Batteries
Transmitter batteries, flight battery, electronics battery if using nitro, glow starter battery, ignition battery if using gas, starter or field box battery.
Full fuel tank
Securely mounted batteries and all other electronics.
Wing and tail mounted securely. Inspect hardware before assembling. If you have never watched a wing come off in flight, it's reaaaaaaallly impressive. The pilot tried a shortcut and destroyed a plane because of it.
Landing gear mounted securely (there's a story with that one)
Switch on radio, then electronics.
Set throttle lock if you have one. Rubber band on throttle works well.
Check control surfaces: Direction, travel, binding, damage, loose hardware.
Check throttle control on nitro/gas. Check direction, travel and freedom of movement.
Check throttle cut.
Good idea from above to check retracts.
Check voltage while operating all the servos together. (checks batteries, checks for potential problem servos pulling too many amps that could lead to servo failure or brown out) I recommend using a voltage indicator on all planes with a separate electronics pack. They're cheap and light.
Make sure prop is tight. (story with that one too)
For nitro, secure plane, start engine and do a good run up. Flitetest review of the Hangar 9 P-51 has a good idea for this.
Check flight area again, check wind direction and have a good time.
I like those other suggestions of things to bring. Snacks and PLENTY of water. Toilet paper. Chairs and a pop up tent usually find their way into the truck whenever I spend a day at the field. Helps to have some shade/rain protection.
Spare parts, extra fuel, tools and GLUE. Folding table. Battery charger. Can't believe I forgot that once.