Avoid camera shake
Hold the camera steady. Use both hands, rest your elbows on your chest and hold your breath as you release the shutter. Take advantage of a wall, post or any other means of steadying support. Use a tripod for shutter speeds of less than 1/60 sec. When using a lens with a long focal length, choose a shutter speed at least as fast as the focal length. For example if the focal length is 100 mm, set the shutter speed to at least 1/100 sec.
As a basic guide, use the "rule of thirds". Position points of interest or areas of colour a third of the way up, and/or along the frame. Putting a point of interest dead centre usually makes for a dull picture.
Use the frame of a doorway, arch, or trees to emphasize the main subject. Try and find a main point of interest, even in a landscape and exclude the unnecessary. Less is usually more. Try to lead the eye through the picture e.g. with a winding road leading to an interesting tree, mountain or building etc.
Light is the photographer's paint brush. For outdoor shots, the best light is found during the first two and last two hours of the day, when the sun strikes at a low angle. But some of the best shots are often taken as the sun breaks through a cloud sky, particularly just after a storm. If you're lucky and have the patience to wait, the sun may strike just the right spot in the scene to make a perfect picture. In outdoor portraits, avoid direct sunlight into the subject's eyes causing squinting. It's far better to use fill-in flash.