I had a quick look at TWIP tonight. One question that Scott Bourne received recently is "I am just getting my first camera. What’s the one thing I should try to remember to get the best photos I can possibly get?"
His response was to shoot with the light behind you. Its astounding but I remember my Aunt providing me with this tip when I was really young. (Like 5 or 6???? I also recall her saying not to try to shoot through glass because of the reflections.) Its such a simple thing and yet, with digital cameras we have somehow forgotten this tip. Or at least it hasn't been drilled into us like it used to be.
Imagine in your mind a building. You are on the north side of that building at noon on a day with a few clouds but mostly blue sky. Are you going to get a reasonably exposed image? Probably not. (Unless you use HDR which is a whole other topic). If you move to the south side of the building, you can then expose the building and the sky correctly. Simple. Important.
A lot of beginners see their subject, and fire. Armed with this rule in mind, even if you have your camera on auto it will be able to handle the scene. The other nice thing about this rule is, once its in your head, you start seeing light differently. You see that hard light from the front kills shadows and makes your subject lose depth making it look flat. You'll see that those last rays of sunlight when cast from the side or at an angle are absolutely beautiful.
While I call it a rule, its a fun one to break now and then. The thing about photography rules is that 95% of the shots you do should follow most of them. When you break a rule, though, make sure its obvious and deliberate. Backlit subjects turn into silhouettes quite nicely. If your subject is backlit you can let it go completely black. The other option is to use some fill flash.