Basic Camera Controls
All cameras, at the most basic level, work the same. They are a light-tight box, that has an opening (the aperture), which is able to be controlled (opened and closed) by some sort of shutter mechanism. The box has some way of holding light-sensitive material, and a way of getting that material in and out of the box.
So, as far as basic controls or usage, the sequence becomes: loading the camera, making an exposure (or series of exposures), then unloading the camera. With a point and shoot, or any automatic camera, that is pretty much it. Gaining more control makes things a bit more complicated. There are a few more steps along the way.
First, we load the camera. With 35mm (135), this involves opening the camera back, usually by pulling up on the rewind knob, or by a sliding release. Once the back is open, the film is inserted in the left side of the camera, with the protruding spool down. The leader of the film is pulled across and attached to the take-up spindle. On cameras with auto-advance, usually the leader is pulled out to some mark. With manual advance, once the film is attached, release the shutter and advance the film until it is around the take-up spool at least one full turn. Close the back. Gently rewind the film rewind until it is snug, then advance the film until the frame counter reaches 1. If loaded correctly, and the slack is taken up by rewinding, the rewind knob will turn as you advance the film. This tells you it is definitely going through the camera. With auto-advance, simply close the back, and the film will advance. If it does not advance in either case, open the camera back up, and redo.
The meduim format is a bit different. An empty spool serves as the take-up reel. The film has a paper leader, which is pulled out a bit, and the tongue of which is inserted into the center of the empty spool. Close it up,and advance to the first frame. Many use film-holding inserts or 'cartridges'. These are a bit more involved, and it would be wise to consult the manuals for proper loading technique. This is really not to avoid the question, but they are different enough that a general description is to be avoided.
Large format cameras use film that is loaded into film holders. The holders each take one or two sheets of film (4x5 usually two, one on each side). There is a dark slide on each side wich prevents the film from being exposed. These usually have a tab that is white on one side and black on the other. There is a set of guides inside the holder, on the sides. The film needs to go under these. Insert the slide so that the white is out, on both sides of the holder. Push them in to just about the beginning of the guides, so you can still see them. Now get the film, and turn out the lights. The rest needs to be done in complete darkness. Open the film box. The film will be in a foil or plastic bag. Open this, and pull the film out a bit. Feel across the top of the film. There will be notch codes cut out. The notch codes go in the upper right corner, as you hold the holder with the open end up. This ensures you have the emulsion side out. Slide the film in all the way, the close the dark slide. Repeat.
Next, for cameras that have meters (SLRs in particular), the film speed or ASA needs to be set. This tells the meter what film you are using. Many newer cameras have what is called DX coding, which reads the speed from markings on the cassette, and set it automatically.
Now it is a matter of composing, metering, setting the exposure (aperture and shutter speed combination) and making the exposure. Continue until the roll is finished. Rewind the film back into the cassette. With manual advance and rewind, there is a release button on the bottom of the camera which much be held down to release the film advance gearing. This is rather important. Hold this down, and turn the rewind handle until it spins freely. You should be able to hear the last part of the film go through. With motor drive, or auto-advance, the camera will usually automatically rewind when the roll is finished.
Now you can open the back and remove the film for processing.