This should be applicable to both painters and photographers — and all other visual artists — with occasional tips for one or the other in particular.
Always love questions, comments and criticism!
UPDATE: I was always skeptical of the rule of thirds/golden ratio, but in this post James Gurney explains a bit about why, and how the eye actually moves. The main thing I neglected to mention in this tutorial is that the eye is scanning for information. All of these compositional things are ways to make the right information more obvious to find at the right times.
UPDATE 2: Wow, thanks so much for the DD! I didn't realise what a big difference it can make. You guys are what inspire me to make tutorials, so if there's anything else you found a little mysterious about art, don't hesitate to suggest it!
Moving out of frame: how is that bad? Not enough to hold attention (nothings happening here, it’s just a plane): I’ve seen lots of simpler things and never noticed any negative effects on my attention. Don’t know what to look at: I’d have thought whatever is in the photo, painting, drawing etc. Looks at the wrong part (eye is drawn to the statue): why is the statue a wrong part? Or the woman? If Hitler was in there as well doing cartwheels and blocking the view of the lovely statue and lady I would still fail to see how that was entirely bad. How are any of these bad? I’m not trying to undermine you. Genuinely just curious.
Our eyes are hardwired to prefer a single focal point, with one or two duller points for context. They process art the same way your brain might process a joke.
1) "Moving out of frame" is like a "knock-knock" setup with no punchline. Where's the car going? 2) "Not enough to hold attention" is the opposite, a punchline with no "knock-knock." 3) "Don't know what to look at" is "knock-knock," then a comment on the weather, then a long story about my childhood, then the punchline. 4) "Looks at the wrong part" is "knock-knock," then news that you have an incurable illness, then the punchline.
In each example, you either feel unsatisfied, get distracted, or focus on something that was unintentional -- and artists usually don't want viewers feeling that way.