Suppose you have something that you want to take a picture of. If you wanted to take a picture of a person, it would be a portrait. Being a thing, this is called still-life photography.
I will assume that you want to take a picture for documentation purposes. Why document objects? If you are a designer, you want to document your prototypes for your portfolio, but there are other reasons, like insurance. Or maybe writing a book about "The Greatest Staplers of the Century" - that would look a bit silly without pictures of staplers.
Size matters
The size of the object conditions the techniques you are going to use. Anything smaller than about an inch falls under the domain of macrophotography, a rather specialized activity. For things the size of an egg and bigger, remember that bigger is more difficult.
Why? because uniform lighting becomes more complex (light falls off with the square of distance), and backgrounds, as they get bigger, become more difficult to control: all sorts of unwanted things, like power cords and shadows, will try to get into the picture.
If you want to take really good pictures of something that is quite big, like a washing machine or a car, you want a studio with a cyclomat and a professional lighting system. Actually, you just want a specialized still-life photographer that has access to all of that. But he will want a lot of your money.
Anyway, onwards to ...
Do not be afraid of getting close to your object. Fill the photogram with it. Try to get a set of "representative" pictures of the complete object, in flat light. Remember that, as in all photography, you know about the object, but the viewer does not. So, don't forget to take pictures of side views, and of the bottom and the back.
As always when doing serious photography, bracket. With digital cameras it costs next to nothing, and even with film it is always cheap, when you compare it to the cost of lost information and the pain of re-shooting. You don't want to be embarassed by your pictures when you do a presentation.
Remember that, to get a feeling of an object, you need at the very list views of its six "faces" (as it where) and shots in perspective. Perspective is tricky; a view camera is tricky to use, but it may just be the thing that saves you.
Having gotten your basic "views", ask yourself "What is interesting about this thing? Is it the textures? The reflections? The way it sits in your hand? The way it looks when it is dirty?". In other words, most objects will have something interesting about them that you want to make visible in your pictures.
This is the moment to take pictures that attempt to convey that point of interest. Again, bracket in abundance.
Context
Notice that some objects make sense only placed in certain contexts. Explore that. If it is a pen, maybe you want a picture in the company of other desk objects. If it is a fruit basket, maybe you want to have at least one picture of it that actually includes fruit.
Remember that backgrounds, and their colors and textures, can make or break the picture.
personal anedoct: I have one picture that I am quite fond of. But Americans don't like it, because the background looks to them like a high school yearbook/Sears portrait background. We don't have Sears in Italy. Nor yearbooks. And that type of background is not much in use. CONTEXT, dammit!
Think of the object in terms of where it is used, what it is used for, who uses it, and try to picture all these pieces of information.
You may also want to play on the extraniation factor. Place the subject in strange and peculiar contexts. Place the watch on the pavement. Put it on an anvil. Half hide the ring into a bowl of ink, and see what happens on film (or on the CCD).
Lighting
In photography, you can roughly distinguish between point light sources and diffuse light sources. Notice that these are not absolute terms: it is the relative size of the light source and the subject, compounded by their distance that makes the light more or less diffuse.
Generally speaking, a light source whose size is comparable to the size of the subject and that is close to the subject will work as a diffuse light source. For an example, place your hand close to a monitor in a dark room, or look at trees under a cloudy sky. Notice how the diffuse light (occasionally called "soft") flattens the surface textures of everything. There is no glitter, water does not sparkle. Metals take on a rather dull appearance. Shadows are soft-edged and even colors appear dull.
A point light source is small in relation to the subject. Good examples are the sun on a clear day, an electronic flash when taking a picture of a sofa, a naked bulb dangling from a twisted cord, hanging from the black ceiling of your existentialist bedroom.
Point light throws sharp-edged shadows. When the light comes from the side of the subject, even minute surface irregularities become very visible (notice: very bad if the subject is your SO). Metallic parts can look "shiny", and all specular surfaces (hubcaps, pinheads, rings...) can exhibit a specular highlight, that's to say a bright point of light - this, in fact, is the reflected image of the light source.
I cannot tell you which light source is better for your purpose. Only you know what you want to bring out in something.
how to improvise a point light source: use a
naked bulb at a good distance from the subject. Notice that, if you have dull reflective surfaces around you (like white walls), they will contribute a measure of diffused light. This is why in a proper photographic studio you always have
matte black walls.
how to improvise a diffuse light source: place a piece of diffusing material in front of any light source; this is called a gobo. As you increase the size of the gobo (I did not make up this word), the light gets more and more diffuse.
Remember to ignore such bullshit as "strobe light is hard". The workings of the emitting source (electronic light, hot lights, candles, the sun, whatever) have nothing to do with its point or diffuse nature; it is all geometry, really.
note: as objects get smaller, it is really difficult to light them with a point light source - as the light would have to be really small. For example, if you have an on-camera electronic flash (source size, including reflector: 4 cm), and you are shooting a picture of a bug (size: 1 cm) at maybe 2 cm from the camera, the distances are already quite comparable.
As an extreme case, you may want to have a total absence of shadows; this is the task for a ring flash on the macrophotography scale, for light tents, and for huge softboxes.
Light metering, exposure, and color shift concepts apply in this context as in all general photography. Just remember that mixed lighting produces color shifts that are horribly difficult (or even impossible) to correct in the printing stage.
Focus is a rather interesting problem. Remember that depth of field becomes small at short distances, an effect that is more pronounced with larger formats. Since working with small DOF can be difficult (unless your objects are all stamps), you will tend to stop down. Which in turn will require longer exposure times, or bigger light sources.
For this sort of work, you really want a tripod with a three-axis tripod head (not a ballhead). Your back and your nerves will thank you.
As the object gets smaller, and you get closer, you will happen upon an interesting phenomenon; you can't focus closer than a given distance, that usually depends on your lens.
When you hit this limit, you have basically possibilities:
If you are getting into this dangerous territory, I probably would suggest a focusing rack as well.
One more technical aspect is focal length; that influences the perspective that ends up in the picture. Generally speaking, a wideangle lens exaggerates perspective (boxes will have falling lines, like skyscrapers shot from a helicopter). A telephoto lens gives a perspective that is closer to axonometry, and emphasizes separation between the subject and the viewer.
In shooting still life, a view camera or at least a perspective correction lens can be very useful. The ability of controlling the amount of perspective distortion, and the extreme flexibility with the focus plane allow precise picture control.
But they are not easy beasts to use.
Involuntary self-portraits
Beware of curved metal parts that will reflect a cute, distorted version of your mug (and camera, and tripod) into the picture. Try to position your camera to avoid that. If it is uncontrollable, you will have to use a light tent and probably retouch the picture later.
A light tent can also be improvised (somewhat) with a large piece of polystirene or white cardboard with a hole for your lens.
Looking professional: the really white background
If you want to "float" your pictures in a page, or to do amusing manipulations with them in Photoshop, it is very useful to have a white featureless background. If you have tried doing that, you will have notice that it is rather difficult; most backgrounds have texture. And removing them is complex. But there is a trick...
Get a nice piece of clean plate glass or unscratched plexiglass. Place it between two tables, or precariously balanced on two chair backs from which it will horribly fall to the ground destroying itself in a million little sharp shards of devastation. Maybe stick to the tables idea.
Place something reasonably white and featureless (a bedsheet, a piece of cardboard) on the floor. Place your subject on the glass.
Now cleverly organize everything so that your subject is in focus and the distant white background is extremely unfocused. That takes care of texture. Now, for the final touch, point a whacking big light on the piece of background that you are using. I said whacking big, but within measure: what you want is to bring the background to the magic number of "+2", that's to say, relative to your subject the background should be overexposed by two stops (a manual camera here will be incredibly useful).
Ok, let me do a boring baffo example. Your light meter (learn all about it in light metering) tells you that your cybernetic hamster device should be exposed at f8 1/15s. Light the background so that it should be exposed at f8 1/60s. There, it became white and featureless.
Notice that if you are using black and white film you may want to overexpose the background even more, to be sure that it goes really white.
But don't overdo it; if the background goes at +5, then you will get flare. This will look like white light bleeding into the subject from the background.
The worthy Ashley Pomeroy reminds me that another technique uses a huge roll of white cardboard. The setup, seen from the side, should be more or less like this:
O
C |
|
S / <-- a soft, nice, curve
---------
/ <-- another soft, nice, curve
|
|
In what is probably the worst ASCII art diagram ever drawn, S is the subject and C is the camera. The other snake-like thing is the white cardboard. All of this is implicitly set on a table.
When the set is properly lit, the background curve will not be visible at all. Remember to keep everything clean.
If you do this sort of things often, there are companies that will sell you all sorts of backgrounds and nifty/practical devices for managing your background rolls and suspending them from the ceiling (the only way to keep sane).
Photoshop is your friend... for a price
It is true that nowadays you can retouch a lot of things in Photoshop, including color shifts and background. Yet, if the picture is out of focus no amount of unsharp masking will add the information that you lost to the modified Gaussian blur of your lens... and if you don't want to try correcting pincushion distortion with Photoshop, trust me.
Consider also the time/money factor. The more you do at the shooting stage, the less time/money you have to expend later to correct the picture.
For batch operations (like generating thumbnails, applying the same color correction, adding a copyright notice) to a set of pictures, learn how to use the Photoshop macro facility.
Or use Image Magick or The Gimp (with perl-fu).
Be Clean
Silly as it may sound, it is important to clean very carefully the things you are going to photograph. Especially if you have shiny surfaces, go over the thing with alcohol and handle it with gloves. Remember that the camera is implacable.
Be particularly afraid of fingerprints and of dust that clings to corners.
Learn from the work of others, then go wild
The photography of things has its masters in advertisement. Study ads. Study art catalogs. Try to reconstruct the lighting setup that managed to create that effect.
Then do your own thing. As always in photography; first technique, then predecessors, then you.
... did I mention that you really want to bracket?