Long time reader, first time poster here. Might aswell try to make it something constructive and hopefully helpful.
My tip: AE lock & Hold
I normally shoot in manual mode, but sometimes it happends that I wander into the lands of Av.
My problem with Av (and any other auto-exposure functions) is that whenever there is a big variation in the amount of light on your subject and on the surrounding scene and background, it tends to either get overexposed or underexposed. Now I can always go in and use exposure compensation, and I will in most cases do that before I even take the first shot judging by the scene. Sometimes I'll go bingo and other times I'll take another shot.
With the 5D Mark III came a rather interesting feature - AE lock and Hold.
Like the normal AE lock function it will lock your exposure, Very handy to use with spot metering in the situation I described above. But unlike it, there is no auto cancel after a set period of time or after the shot is taken. It will simply lock your exposure untill you press the button again and unlock it. Fancy, eh?
The function can be set in the custom controls panel.
Video explaining it:http://youtu.be/DY5LPX52d70