I'd like to add onto what dubge said:
1: Always always always carry a micro-fiber cloth with you so you can clean your lens without scratching the glass (the cotton fibers in your shirt are actually sharp, and if rubbed strongly can cause some scratch damage.) Do this everytime you go to shoot pictures as even a slight smudge can ruin the quality of a shot exponentially.
2: Hold the camera as still as possible. Having an onscreen shutter button helps (2.2 Froyo or download Vignette.) If you're going to shoot without an onscreen shutter button, make sure you take your phones case off first (if you have one) because it will interfere with your finger pressing the shutter button.
3: If you have lots of light like on a sunny day, go into your camera settings and set the ISO to 100. Auto works ok as well if its really sunny and bright out, but if there's even a bit of darkness in your shot, say under the shade in shadows, it will set to a higher ISO and give more grain and noise.
4: Always use the scene called Auto for taking shots of things more than 8 inches away. For anything that close or closer, use Macro setting.
That's about all there is to know. This phone has excellent photo-taking capabilities. Just follow these tips to get the most of it!