[G2 and Desire Z Q&A, Help & Troubleshooting] redpoint73:
I don't know of a guide, and I don't do a lot macro photography in particular, but I can give some general tips. I don't even consider myself much of an amateur photographer, much less any kind of expert. But I know a thing or two about general photography, that IMO make a big difference, and a couple tips useful for the G2/Vision in particular.

1) First and foremost, get some basic understanding of how cameras work. IMO this is the number one reason for crappy pictures perpetrated by the huge majority of people with digital cameras. In particular, learn about the exposure triangle. http://www.digital-photography-school.com/learning-exposure-in-digital-photography. You don't have control over aperture and shutter speed on this phone, but knowing what they are, and how they affect your photo is essential to knowing why a photo turns out good or bad (and how to make more of them "good"). You do have control over ISO, so get some understanding of what ISO means (which leads to the tip 2).

2) Set ISO and White Balance manually, if you have time. I know its an inconvenience to change these for each different environment. But if you have time to do it, it really helps. Keeping these on "auto" seems to extend the amount of time it takes for the image to be captured and leads to more motion blur (presumably, since the AI is taking time to do light readings and calculating the "best" settings). Also the settings it comes up with are not always very good, for instance the phone misreads the light type sometimes, and comes up with funky white balance settings.

Use as low an ISO as possible but still controlling motion blur. Higher ISO leads to more noise (analogous to grainier photos with film). But using too low an ISO forces the shutter to be open longer (to let enough light in to capture the image), which increases the chance of motion blur from either the subject moving, or camera shake. Its a matter of finding a balance between the two.

With lots of sunlight, or even partial sunlight, use a low ISO. 100 or 200 is often more than sufficient for daytime photos outside, even on a cloudy day. Indoors, you will have to increase the ISO much higher. Obviously depends on how many lamps are around, and how bright they are. But artificial lighting is much less bright than sunlight than you think. I often go to ISO 800 inside my house (when no sunlight is coming through the windows).

3) As mentioned in the previous reply, avoid flash. Flash is ok for the moments where you absolutely need to capture the shot in a low light "spur of the moment" situation. But for most situations, no flash with high ISO looks vastly better. The flash bathes the subject in a ghastly artificial LED light, overexposes the foreground, and causes the whole background to be underexposed. Just horrible. No flash and high ISO means the shutter will be open longer. But as long as the subject is not moving too much, and you keep the camera still enough, you will get a much nicer photo.

You'll notice that professional photographers will almost always use separate sources of light, or an off-camera flash, and seldom the on-camera flash. The on-camera flash on most all cameras are bad, and in particular the tiny flash units on camera phones are awful.

I heard of a study, where people were polled after viewing a set of Match.com type profile photos. Overwhelmingly, people indicated that the pics taken without flash looked younger and more attractive than the ones taken with flash. Despite the fact that some of the photos were of the same person!

4) Also as mentioned in the previous reply, the more light the better. From the last 2 tips, this would seem obvious. But there is a lot more subtlety to this than most people realize. Simply shifting the angle of the camera, or changing your position by a few feet can greatly influence how much light is entering the lens. One good example is light sources behind the subject, especially windows during daytime. Too much bright light from the background will make the subject underexposed and dark. Getting windows out of the frame of the photo can turn a throw-away shot into a real keeper.

Don't take for granted that cameras work the same way your eyes do, because they don't. Remember the exposure triangle, and use it to your advantage.

5) Brace your camera when possible, to reduce camera shake (especially in low light). In absence of a tripod, be inventive. Prop your elbows on a table, or even put the camera on the table, if you can do so without the table being in the shot. If there is a wall or column nearby, put the side of the camera against it as a brace.

6) Tap the screen to focus. Most of us with Sense know about this feature, but don't use it as much as we should. Aside from portraits, the rule of thirds (http://fixaphoto.homestead.com/digitalcameratips.html) says the best composition often results from the subject not being in the center of the shot. Therefore, since the "normal" auto-focus of pressing the shutter button halfway is center weighted, its sometimes not going to focus on the subject. So tap the screen on the subject before you take the shot. You often won't need to do this, but it can help sometimes.

7) You can force the exposure darker or brighter in Menu>Image adjustments, if you just can't seem to get the exposure right for a given ISO. One example is taking night photos, where you want to focus on streetlights or headlights. The shutter will stay open a long time, and the image will often look much brighter than you intend (and brighter than how you see it with your eyes). You can force it darker by changing the exposure. Again, not something you will often need, but once in a while can make a huge difference.

8) Practice practice practice. Every one of the tips above requires lots of practice and experimentation. With digital cameras, you really can take as many pictures as you like. You're going to end up with a ton of photos to delete. But this is really the only way to learn.

The camera on our phone certainly is not the best. The largest complaint seems to be that HTC phones over-process and create too much noise in the photo. But with the proper technique, it can take decent photos. Hopefully my tips are helpful.