Learn about composition, light, exposure and depth of field. Then practice by always thinking about the light, the composition, the exposure and how much or how little depth of field you want. Doing this will help you avoid falling into what I call the "machine gunner mentality" – take 300 exposures and hope – HOPE – a few are worth saving. I’ve no doubt someone will tell you to: "Just go out and shoot and shoot and shoot and shoot. That’s how you gain experience." This is about the worst advice you can get. The only "experience" you’ll gain is in taking snapshots. Good photography requires thinking – thinking about your composition, thinking about the light, thinking about the exposure, thinking about depth of field. Since thinking requires time there is no way to be thinking about those elements if you fall into the "machine gunner mentality". The goal should be quality, not quantity.
Here are some sites you should spend time on:
http://www.digital-photography-school.com
http://www.kamerasimulator.se/eng/?page_id=2
http://www.photonhead.com
http://www.illustratedphotography.com/photography-tips/basic
http://www.dofmaster.com/dofjs.html
Another technique you need to learn is to pay as much attention to everything else in the frame as you do to your main subject. Look for litter, power lines, dead branches, an overexposed area in the background, a dull sky – anything that might be a distraction to someone looking at your pictures. By doing so you’ll learn that a slight change in your composition can eliminate or at least minimize any distractions.
http://www.flickr.com/drifter45h/3991210245/ After settling on this composition but before releasing the shutter I picked up 3 cigarette butts, a discarded tissue and a plastic bottle.
Don’t fall into the "Oh I can fix it in Photoshop" mentality either. The idea is to "Get it right in the camera" and keep your use of an editing program to a minimum. An image file that suffers from a blurry image caused by subject or camera movement or is underexposed or overexposed or is out of focus is a lost cause. You might be able to improve it if its only slightly under or over exposed but if its out of focus or blurry all you’ll be doing is wasting your time.
So learn to concentrate on the light, the exposure, the composition and the depth of field and learn to pay attention to everything in the frame.