For most situations I compensate to the left (under-expose) by 1/3 stop to 2/3 stop (if sunny) because shooting at the neutral position blows out the highlights (11 year-old camera with DX sensor). That is probably not necessary if using a superior-quality FX sensor with an inherently greater exposure latitude. The leftward compensation also boosts my shutter speed, which was a necessity when using my old 70 - 200mm w/o "IS". Every little bit helps with that lens. My 300mm has "IS" but I still need to manage the highlight issue. Shooting into an overcast sky I will compensate to the right by at least 2/3 f-stop, sometimes even more. My thoughts are constantly on the move, often by circumstance, and therefore failure to return settings to what passes for normal territory after skewing them on some flight of fancy is a mistake I am doomed to repeat. Sometimes I even accidentally come in contact with a control knob and really screw things up, like going from Av mode to some other setting and not being aware of the change until I lost the shot. I've gone out with a dead battery, or gone out with the battery still in the charger back home. That's what happens when one is subjected to constant interruption. When stuff like that happens I try not to lose my cool and keep reminding myself that I'm lucky to even have a camera, or a telephoto lens, all the result of gifts and therefore try to do my best with what I've got. I could just as well have no camera at all, at least not one from the digital age.
