Canon 24-70mm F2.8 USM L, ISO 200, F5, 1/250th, Canon 580EXII Speedlight in E-TTL II mode

Canon EOS-1D Mark III @ 46mm, F5, ISO: 200, 1/250th
This one caught me out many times when I started out. In daylight it's not going to be a problem but when you're in a situation where you dont want to use a high ISO and want a low noise but well lit image you'll be using a flash and it's important to look around for anything reflective behind the subject ( namely windows and mirrors ! ) or you too could fall victim to a nice dark image with a bright flash bang in the middle ! The solutions arent to hard though. You can move your subject to a place where there isnt a reflective background or in the cases where this just isnt going to be possible, crank up the ISO levels until you're getting the shutter speeds you need ! It's also worth mentioning that when you're using a flash to set your WB ( white balance ) to the flash setting as it makes a huge difference to the accuracy of colours.
Canon 85mm F1.2 ii USM L, Variable shutter speeds and ISO's.

Canon EOS-1D Mark III @ 85mm, F1.2, ISO: 50, 4/10th
Here is a basic guide to the tried and tested " mirror self-portrait " I did it on an overcast early evening to highlight the problems us photographers often face when we lose our favourite and useful element - light. Obviously being a mirror, flash is out of the question ( see above ! ) So in low light, we're limited to increasing the ISO and incuring the wrath of image noise or finding alternate light sources. In many cases a simple lightbulb will make a world of difference. On a nice sunny day of course, this will never be a problem. You can choose your F numbers freely with no real worry of image blur. In fact taking a mirror outside on a sunny day gives you the freedom of choosing any background you want ( just make sure you dont use the sun unless you expose the shot for your face ! )