The primary concepts you need to think about when designing an image in your mind are:
- Balance - symetrical or more pleasing to the eye, asymetrical. All images need to be in balance to work well
- Consistency - this applies across a whole range of aspects, whether working on a series of pictures or in the visual treatment of a single image
- Contrast - this is a wonderful element to play with and an essential part of design
- Proportion - the relative size of objects but also the relative importance of visual elements
- Proximity - this is the single most important design concept for creating meaning in an image. Two elements close together will effect each other's meaning in a fundamental way
- Simplicity - keep it simple. Single concepts work best. Try to say too much and all messages get lost
- Unity - this can apply to the overall colour tone, to the harmony in shapes across the frame or the relationship of elements within the image
The above are some of the most crucial mental building blocks for design. Look through your images and those of other photographers and consider each of the elements above. I've given some clues as to how you may interpret the concepts but there are many more ways to apply them. So get that brain into gear.
But for heavens sake don't try to be thinking of all of this stuff when you take an image. It will just inhibit you. The key is to look, learn and absorb information like this until it becomes intuitive. In the same way as driving a car becomes automatic, you don't have to think about changing gears, the clutch etc, you just do it. However it will sharpen your mind and your ability to be aware of what you are doing so you're really looking where you're going rather than just guessing and driving blind (if I may labour that metaphor one more time).
Plenty more ideas and advice to come. Stay tuned.