Enlist a Family Photo Coordinator
Consult with the bride and groom to select a responsible member from each side of the family to help corral both families when it comes time for large group shots. This is especially helpful if the wedding reception is attended by a lot of people. If you do not personally know the parties in attendance, attempting to gather the masses yourself can be frustrating.
Visit the Location Beforehand
By visiting the location of the reception in advance, whether it be on a sunny beach or the dim interior of a local church, you'll know what to expect in terms of available light. This will allow you to pack the appropriate gear for the occasion -- for example, fast lenses and flashes for low light or shade panels for situations with high reflectivity. Acquainting yourself with the setting will also allow you to formulate ideas for shots, providing you with a mental blueprint to work from during the actual reception. You will also know what equipment to use when and where, so the guests will not have to wait too long for you to get set up when you want to take their pictures.
Keep a Stocked Kit
There's nothing worse than digging in your bag for a blank memory card or an extra roll of film only to find that your stock has run dry. Avoid a trip to the local camera shop by packing more media than you think you'll need -- that way you'll be able to focus on the action at hand without any lingering paranoia. Also bring a variety of different lenses. A wide angle lens, less than 35 mm focal length, is excellent for fitting in a lot of action, such as a dance floor or the entire altar. A telephoto lens, greater than 80 mm, makes a great portrait lens for more intimate captures.
Think Outside the Box
Every wedding album contains the archetypal shots: bride and groom with both parents, shots of the best man and bride of honor and a shot of the couple's first dance as man and wife. These are great to include in a traditional sense, but don't ignore your creative side when shooting a wedding reception. Use the small details -- light falling onto the pages of a filled guestbook, a private moment between the bride and groom, or the happy tears in the eyes of the attendees -- to create photographs which convey a sense of mood and presence. Shoot candid photos to avoid being obtrusive, but also to capture beautiful fleeting moments.
Shoot A Lot, Then Shoot More
If you're using a digital single-lens reflex (SLR) camera, you have the ability to take as many pictures as your memory cards will hold. There's no such thing as overshooting at a wedding -- any extra or duplicate shots will serve as insurance for the ones you missed or that did not turn out so well. Also, try shooting the important shots in RAW format rather than JPEG. This will give you a very high quality, uncompressed file which can be edited to perfection.