Choose the right camera. Cameras come in many styles and forms these days. Anything from low resolution cell phone cameras to professional DSLR and Medium format cameras, and you can still find many great quality film cameras as well. Determine what the camera will be used for, and select your camera accordingly.
Understand lighting conditions. There are many books and magazines printed solely on this subject. Read some, and learn what color temperature means. Learn what f-stop means. Learn what depth of field means and how to control each of these things.
Understand exposure. Quality photographs require more than just pointing a camera at a subject and releasing the shutter. One needs to understand exposure controls, what ISO or ASA means, and what shutter speed means. If using a flash, one must know how to balance the amount of light generated by the flash unit so as to expose the subject correctly without affecting the background.
The term correct exposure is one that is subjective in every sense. What may appear to be under exposed to one person may be perfect for another. It is all about what you think is appropriate, and if you are a professional photographer who sells your images, what the buyer thinks is appropriate.
Experiment. When setting up a shot, expose it at what you think the perfect level is. Then adjust it and expose a new shot with darker settings. Then do it again at brighter settings. This is called bracketing. Many professional photographers bracket every time they shoot.
As you gain new skills, constantly push yourself to try something new and venture out of your comfort zone. Always push yourself to be better.
Keep in mind the need to have a reason (theme) for taking a photograph – think about how to compose your shot. Remove distractions, focus on the subject, check exposure, check depth of field, monitor ISO / ASA, and shutter speed. Do these things right, and you will be well on your way to producing better images.