The camera. If you're serious about good photos, you won't pack a disposable camera on the trail. Like discount-store bikes, cheap cameras just can't handle the job.
I recommend an SLR (single-lens reflex, where the viewfinder actually looks through the lens, not through a second peephole), with a zoom lens. A 28-80 zoom lens isn't too pricey, and will take almost every photo you need. You can quickly frame your photo using the zoom. If you plan to shoot flowers and small details (bugs and insects) the lens should also allow macro focusing.
The camera should be smart, but it shouldn't think it's smarter than you are: It's nice to have autofocus, but you should be able to focus manually or lock the focus while awaiting some action. You should be able to easily control the exposure manually, for example, to specify a shutter setting. (When the bike has major speed, your shutter can't be slow.)
The film. Your film is an emulsion of chemical particles. (When the particles are hit by light of certain wavelengths, the chemical changes. The developing process converts this chemical change into colored dyes within the emulsion.)
The speed with which a film reacts to light is called an ASA or ISO rating. A higher number means the film exposes more quickly (with less light). To make the film expose with less light, the individual particles are made larger -- grainier. That's why you want to use the slowest (lowest ASA number) film that you can.
"Slower" film -- lower ASA number -- has more (and finer) particles in the emulsion, and can provide richer colors plus more subtle details. It's also more forgiving if you don't get the exposure absolutely perfect. But the slower film may not expose properly when you're forced to use a fast shutter speed (see below) in low light. Telephoto lenses also reduce the amount of light available, so a faster film may be required.
ISO 200 is a good compromise for typical biking photography. And for any ASA rating, print film is MUCH more forgiving of imperfect exposure than slide film.
Get the exposure right. Or, at least close. Think you'll just let your camera's microprocessor handle everything for you? Think again. To get the picture you want, you often need to override the automatic settings. So you need a camera that lets you take control.
You have two
variables to consider:
Which of these variables is most important? It depends on the type of picture you'll be taking. For rapid action photos, you want a fast shutter speed to freeze the action. But for landscapes, you'll want to keep both foreground and background in focus. To do this, you must make the lens opening as small as possible, so you select a larger f-stop. When "depth of field" is important, the size of the lens opening may be the most important variable.
Once you've decided which variable is critical, you set it, and let the other one change to get the right exposure. For example, if you narrow the lens opening so less light enters the camera, you reduce the shutter speed (so the film is exposed longer) to compensate.
So as you read the numbers on your camera, the principle to remember is:
The focus. Of course, all is lost if your image is blurry in the final photo. The light needs to be bent precisely so every ray that leaves a particular spot on your subject strikes at one tiny place on your film. If your subject is far away, the light rays arrive at the lens traveling nearly parallel. A bit of bending puts them all on the same spot of your film. If the object you're photographing is closer, the rays of light are spreading out more. These light rays must be bent back inward to a greater degree so they can meet at the same spot on the film. The camera's focus adjustment moves elements within the lens so the light rays are bent precisely for whatever distance you set. (With cheap cameras, the focus distance is set. This means that these cameras will give you a blurry image when shooting close-up.)
The camera's f-stop setting affects how much is in focus -- called "depth of field." If the opening behind the lens is smaller (high f-stop number), there's less light, but the light rays that make it through the smaller hole are traveling more parallel. Therefore, for light waves originating from different distances away, the amount of bending required is more alike. So the focus is less critical, and more objects will appear in clear focus.
Conversely, when the aperature is wide, the focus must be more exact to be sure the object you want to photograph is crisp in detail.
Focus (and the depth of field) is also affected by the type of lens you're using. Telephoto lenses and macro lenses are the most sensitive -- they must be focused very precisely, because the depth of field is very narrow. On the other hand, wide-angle lenses give much better depth of field. So if you're wondering whether you'll get a rapidly-moving biker in focus, dial your telephoto back to a wider field of view.