This guide will answer these questions. I'm an academic who has interviewed lots of shelter and rescue workers, taken lots of pictures, and read lots of things so I can help you maximize both your time and the chances of your animals to be seen, supported, and adopted.
Step 1: What's a good photo anyway?
Good photos have the animal in focus. Good photos do not include cage bars. Good photos avoid red demon eye. This is not as easy as it sounds. Some general tips.
1. Give yourself ten minutes with the animal and expect to take a lot of photos. But don't take more than fifteen minutes--you're busy, and sometimes the animal just isn't feeling it. Coming back hours, days, or a week later will make both your lives happier.
2. Having two humans makes photo-taking much easier. Get someone to help you quick or have volunteers take photos in pairs. That way one person can concentrate on soothing the animal, keeping their attention, and making sure they don't bolt out the door and over the field while the other can focus on the pictures.
3. Take dogs and outdoor animals outdoors. Position cats and indoor animals so they're facing a window or other light source. This helps put a shine in the animal's eye and saves you from needing to use a flash--the prime cause of demon red eyes.
4. It's easier to get animals in focus when they're not moving. If you can, tire the animal out and then take your photos. You can also try using the "sports" or "action" setting on your camera, if it has one, to capture quick motion.
5. It's also easier to get animals in focus when there's no cage bars in front of them. Bars freak out the camera and often cause it to lose focus on the animal--another good reason to take animals outside or move them from a kennel or cage for their photo.