Unless you are working on an artistic piece, the ultimate goal of lighting a set is to make it appear as though you are working in broad daylight. This means every aspect of your object is lit from all angles so that no dark shadows or bright spots distract from your shot. Many studios are rigged with dozens of lights on the ceiling that can be manipulated any which way you need them; however, you don't need a professional setup to create proper lighting. All you really need are three basic lights. A three-point lighting setup includes a key light, a fill light and a back light.
Your key light is normally your main light. This light should illuminate the object from the front at an angle coming in from the left. It should be your brightest light. Your fill light is normally less intense than your key. It is meant to fill in any shadows that your key creates, so it should be placed in front of your object, as well, and project at an angle coming from the right. You can use a bounce card or umbrella to diffuse your fill light. Simply aim the light at the card or the umbrella so that it angles off of it and hits your object at an angle from the right.
Now that you have your object fully lit from either side, you can finish it off with a back light. The back light should come in from behind the object at an angle facing downward. The light should be placed up high so that any shadows it creates will be out of your shot range (normally near where the camera is.) Remember to always use the same type of light. For example if you have sunlight coming in a window, you don't want that sunlight to mix with a halogen bulb. If this is the case, you will need to close off the window and use all of your own lights. Similarly, if you are in a room with fluorescent lights, you don't want to mix in other kinds of lights.
You can play with your lights to see what other kinds of moods you can create. For example, working with just a back light will give your object a silhouetted effect. Placing a bulb on the ground in front of the object will give it an eerie glow. You can use less light to give your photo or scene a realistic feel. The more you play with your lights, the more you will learn about lighting.