The PHD Guide to Photography with Disposable Cameras

Here are some tips that may help you with your photography:

Even disposable cameras can produce good photos if certain aspects can be controlled. Here are some common causes of ruined pictures:
Blurred--camera movement. Need something to steady the shot. Try leaning against a wall or on a table to steady the shot. Also, press the trigger as a gentle squeeze rather than as if it weighs a ton.
Picture too dark--flash or some other lighting should be used. Also, your finger, camera strap, or hand may be blocking the flash.
Picture blocked--perhaps your finger or the camera strap is in front of the lens. Be sure to hold the camera properly and keep the lens strap behind the camera.
Sunny day, but faces are dark and can't be seen. Use flash on sunny days. This is called "fill-flash" and it compensates for the shadows on people's faces and can also compensate for "back-lighting" when the light source is behind your subject.
Everyone in the photo is squinting. Don't have them looking directly into the light source. Have your subjects look at an angle from the light source. Also, use fill flash.

According to a news article a bunch of years ago, 10 mistakes caused U.S. photographers to waste all or part of an estimated 108 million rolls of film annually. That's 15% of the 700 million rolls of film processed each year in the U.S. (Of course, with the new digital cameras, a lot of these problems can be eliminated and you can check your exposure and retake the picture if there's a problem. -- But still, these tips will be helpful if you still want to use a disposable film camera!)
 
The top ten mistakes:
--Underexposure -- maybe higher ISO/ASA Rating could be used. Flash might also be an option. Better lighting also would help.
--Improper storage -- leaving a film camera in the car during the summer cooks the film and affects the chemicals in the film emulsion. Keep the film/camera in a cool, dry place.  If you must leave the film/camera in the car, keep it in an insulated lunch-box style container.
--Fluorescent lighting -- produces a weird green effect and other strange colors on the final images.
--Blank rolls -- sometimes the auto-rewind is triggered accidentally, resulting in what looks like an "exposed" roll, which is then taken to be developed. 
--Overexposure -- wrong type of film. Too high of an ISO/ASA. Using indoor rated film in the outdoors.
--Film advance -- sometimes either a mechanical problem causes the advance to jam, or strips the gear-socket holes in the film. Then the film doesn't advance properly.  Also, if the film wasn't loaded properly, it won't advance through the camera. You may be taking pictures, but not on the film. This results in the "blank roll" syndrome as well.
--Flash synchronization -- if your flash isn't "synched up" with what you want to get a picture of, you'll miss your shot. Not so much with the old film cameras (although if you chose the wrong camera shutter speed, you'd miss your shot). With some of the digital cameras, there's a delay between when you press the "shutter release" and when the flash eventually fires. You again might miss precisely what you wanted to get a picture of. 
--Tungsten lighting -- the wrong film or camera setting results in bizarre colors on the resulting images.
--Object on lens -- whether it's dust, stray leaf, dog hair, mud splatter, or fingerprint, it will affect your resulting image by either blurring it, or totally obstructing it. So make sure your lens is clean (even if you are using a disposable camera --they get dirty, too, you know!).
--Out of focus -- with disposable/fixed-aperture cameras, if you are too close to your subject, you are out of the "focal range" and your image won't be in focus. If you have an autofocus camera, and if you are shooting through a window, the "autofocus" might be focusing on the window rather than on the scene you want to capture.

Here are some additional reasons why film gets wasted or photos are not quite as good as they could be:
-- Not holding camera steady
-- Flash directly into a mirror/window (the flash reflects directly back into the camera--obliterating the photo)
-- Accidently firing shutter/camera because shutter is cocked/wound up
-- Lens cap on
-- Flash not ready to fire/not turned on
-- Stuff cluttering background
-- Too far from intended subject