Remain Overstocked
There is little worse than running low on film or reaching your last memory card's capacity just before the couple's dance at the wedding after party. Before departing for the occasion, ensure that your bag is stocked with more media (rolls of film or memory cards) than you think you'll need. If you think you'll shoot at least 10 rolls of film, bring 15 or 20 for insurance. If you're certain you'll fill all four of your memory cards, pick up two additional ones at a photography retailer en route to the wedding. If you're shooting digital, bring along extra batteries as well.
Use Multiple Cameras
Bring along your most reliable camera, affixed with your favorite lens, for the important shots (walks to the altar, vow-taking, first dance). Also carry another camera which bears a wider lens to capture candid or less formal moments. Using two different cameras will provide diverse, visually exciting results -- as if two photographers were covering the event rather than just one. A second camera is also another insurance measure in case your primary device should fail. Experiment with lenses of different focal lengths (a 28 mm lens on one camera and an 80 mm lens on the other) for a varied body of work.
Be Bold
The timid wedding photographer often ends up with mediocre shots. These shots may be disorganized or chaotic, with people looking in a number of different directions. They may also be too distant, creating an alienating sense of space within the frame. Adopt an air of charisma and boldness while shooting. Get up close to people without being too obtrusive, arrange them as you see fit, and thank them for their cooperation. Your goal should be to document the wedding in its entirety, not to take snapshots of it from the sidelines.
Look for Light
Too often wedding photographers rely on artificial flash to light their scenes. While an external flash unit may serve its purpose, the resulting photos are often too bright and devoid of detail. Before mounting your flash, try to make use of the available light pouring through the windows or the warm glow from the overhead chandelier. This type of diffused lighting flatters all skin tones and adds an intimate, natural mood to the picture. When artificial light is necessary, use a unit with an adjustable head. This allows you to bounce the flash off of another surface -- a ceiling or reflector panel -- to create a softer, more diffused effect.