This next tip came in one of my mailings this week and  is only really useful if you have program modes or manual options on your camera.  So, mainly you dslr folks.  

Stanford has some new app's that help you visualize the exposure triangle at work.  You can manipulate the aperture, ISO, and shutter speed online and see how the image is affected immediately.  You can see how much of the image is in clear focus, how much is lit properly, and when parts of the image become over- or under-exposed. 

Fun. : )