I wrote this in response to a thread posted here by raykart. There's a lot of information in this section about technique - rendering, anatomy, lighting, colour theory, etc. - and less concerning some of the more basic elements involved in crafting an image. This was put together very quickly, but a couple of people have mentioned that the information was useful, so I thought I'd repost it here.
Raykart's image -
My reply -
Composition. It's hard to create an interesting, dynamic image with your subject so central. Look at the attatched image. The pic to the right of the original shows your basic arrangement - a central subject with a symmetrical frame on either side. Not very exciting. But your composition doesn't have to be complicated to be interesting - in the pic to the right of that, I've simply shifted your subject away from the centre, and added some foreground to balance it out. If you have trouble establishing your composition early on, or struggle to break away from symmetrical arrangements, try laying out your image on an oversized canvas then cropping down once all the elements are in place; that'll give you the chance to try different things to see what works.
Design. Your bot looks awkward. That's partly because of his stance, but the design is inconsistent - you're mixing circles and oblongs and large and small masses, as I've tried to indicate with the purple outlines. An easy way to avoid this is simply to base your designs around a single shape which repeat throughout the design. It's a pretty crude approach, but it's a good starting point. Notice that even though my bot ( in the middle ) is very simple and is made of different sized bits, he looks consistent because of the repeated curves. The next pic shows that bot dropped into the altered composition.
Narrative. Your pic has a nice mood to it, but it really isn't telling us anything. There's lots of simple things you could do to add interest here. On the bottom row, I've put in a few examples. First, I've dropped the camera to really show off the size of your bot - you can exaggerate this further with some atmospheric fade, pushing the bits that are furthest away from the viewer towards the background colour. Next, I've dropped in some birds, a cheap trick to push his scale even further, and added some little critters to the foreground blob, which has now become a branch. Why are they there, what are they doing? It doesn't matter as long as it prompts the viewer to ask some questions and get involved with the story surrounding your image. Finally, I've re-introduced the backlight from your original - that will help set up an evocative mood and be a useful way to add definition to such a simple composition.
In my opinion, this stuff really is the most important part of our craft. The bones of your image. Get this right, and the rest of the process will be much easier - your painting should 'work' even if, as above, you only spend five minutes scribbling it out.