I've been using digital cameras of various types for about 7 years now; I have learned a great deal on the way and I have no doubt whatsoever that I will learn a lot more. Here's a few things I've picked up on the way: …
Megapixels are the least of it. Despite this, they are the number one selling point. It's easy to see why; the manufacturers simply raise the number and it's clearly better because it's higher. Marketing is such fun.
Megapixels do count, especially if you are going to crop and/or blow up your picture to some huge printing size, but they count a lot less than the quality of how each pixel records light. Ideally you want a pixel that faithfully captures the incident light in terms of both color and intensity. Higher pixel density chips (especially those in point and shoot cameras) have a harder time with this, meaning that more light sensitive settings (higher ISO values) introduce a lot of noise – wrong colors at wrong intensities.
Lenses are the most of it. A good lens is the single most important factor in getting a good quality picture. By a good lens, I mean one that delivers a sharp image, and is relatively free from faults such as chromatic aberration, distortions such as pincushioning and barrel distortion. A zoom lens with these qualities is usually expensive, a fixed focal length (prime) lens much less so.
For digital SLRs, camera body is less important than the lens. You can spend a lot of money and get ever more sophisticated control over your image, but the difference is not huge.
A tripod is essential for a really good photograph. Even with anti-shake innovations such image stabilization (either lens or camera body), it is very hard to eliminate shake from a handheld camera. A monopod helps a bit but a tripod is the best. Cheap tripods don't really do the job; you need to spend a bit for a rock steady mount.
Shooting in RAW format allows the greatest control over your image. The downside of this is that the image files you collect are very large. But you have the opportunity for considerable post-capture image processing in terms of color balance and tone, sharpness, and noise removal and have not lost any data from your original frame (as you will do if you set your camera to record jpeg format files).
The colors and tones that I really like in my photographs are not the most popular, but that's ok. I feel I have found a style that is somewhat my own.
Most important of all, it continues to be fun! If it ever stops being so, then something will have gone wrong.