You Must Remember This...
Minimum shutter speed = focal length of lens
Shorter focal length lens = more depth of field
Use A or Av mode when you want to manually set the aperture to control depth of field
Use S or Tv mode when you want to manually set the shutter speed to stop motion
Shutter speed of B or Bulb = shutter open as long as you hold down the button (use a tripod).
Use fill-in flash exposure adjustment of - 2/3 when shooting portraits outside.
Print this page and cut out the above quick reference guide to keep in your camera bag.