Once you have your camera ready for shooting pictures (see my ideas for a pre-shooting routine here), there’s a bit more to getting a good sho than just looking through the viewfinder and pressing the shutter button. There are two general ideas to keep in mind.
First, are the camera settings right for the picture that you want to take? If you have your camera set to one automatic mode or another, the picture should come out with an acceptable exposure. If you’re controlling the exposure yourself — by specifying an aperture, for example — check in the viewfinder or on your camera for confirmation that the shutter speed and ISO will react for a picture with good exposure. If your subject is moving, is the shutter speed set fast enough? If you want to isolate your subject from a background that isn’t important to your picture, you want a wide aperture (low f-stop); if you want everything in the picture in focus, you want a narrow aperture (large f-stop). If you’re using a longer focal length, it will be harder to hold your camera steady and you’ll need a faster shutter speed to achieve a sharp image and avoid blurring throughout the picture.
All of that is a lot to keep in mind when you’re taking pictures, and you don’t want to spend so much time thinking through your camera settings that you miss the opportunity for a good picture. (It’s absolutely certain that the picture won’t come out at all unless you press the shutter button.) Practice taking pictures with your camera so that its operation becomes second nature. Settle on an exposure and other settings ahead of time, or use a “scene mode” that fits your surroundings. When in doubt, just press the shutter anyway. The memory card in your digital camera will hold countless images, it’s easy enough later to discard those that didn’t come out well.
Second, will what you’re seeing in the viewfinder actually look good as a picture? The most common problem is stray or random material that will detract from the finished product. Maybe there’s a post that your own eye ignores (you’re captivated by your daughter’s smile) but anyone else would see as a distraction because it looks like it’s growing out of your daughter’s head. Or there’s a power line drooping across the top of your picture, or shadows that your brain ignores but will make the photograph look strange. If you catch these problems when you’re composing a picture, there may be a simple solution. Take a couple of steps to the side, for instance, and the tree no longer grows out of your daughter’s head. Turn your subjects, or have them move into the shade, and ugly shadows may go away. Take a few seconds (if you have them) to detach yourself from your primary subject and scan the viewfinder for distractions, and you’ll wind up with cleaner and more interesting pictures.