Orb photos
Orbs are believed by some to be spirit energy. Most of the time they're just nothing.
"Dust orbs"
It is important to keep your camera lens clean. A dirty lens can make it look like there are orbs everywhere. Don't take pictures while walking down a dirt road or while moving about in a dusty room, because you will be kicking dust up into the air. Remember that just because you didn't see any dust in the pictures you took right before and right after you got an orb pic does not mean there was no dust. The dust was there, it was just out of frame.

Precipitation
Don't take pictures in any kind of precipitation. Even when it has just stopped raining, there's still moisture in the air and the water droplets can look like orbs. This is a picture of snow.

Mist photos
If you're taking a picture and it's cold out, hold your breath so it doesn't show up in the photo. Also, don't smoke or light candles when taking pictures. Moving rapidly from a cold to warm temperature may cause condensation on the camera's external and internal surfaces, which can look like a mist. The photo below is of breath in front of a camera on a cold night.

Camera straps, body parts in view
Be mindful of your camera strap, finger, hair, or anything else getting in front of the picture. These can look like anomalies when illuminated by the camera flash. Here is an example of what a finger can look like.

This is a camera strap...

And hair...

Camera problems
You should read through your camera's manual so you know when you're doing something wrong, and you can become familiar with all the different kinds of camera defects.
Long exposure time
If someone walks quickly by the camera with no flash and a longer exposure time, the result will be a semi-transparent image that looks like a ghost. If they're wearing black, they will look like a shadow person.

They can appear to be missing an arm or a leg, because they're moving so fast.
