There will be hundreds of special moments on the wedding day that you as the photographer must notice and capture. Certain events, such as the vows and walking down the aisle cannot be repeated, so give yourself a good position in the venue to begin with, but also keep out of the way. A nice effect is to use the slow sync flash mode, so you capture the blur of the couple walking, but the center of the frame stays sharp because the flash freezes it. Turn the mode dial to TV or S (Shutter Priority) mode and use a slow shutter speed of 1/4th of a second. Use either the on-camera flash or a separate one for more power. When you use slow sync, the shutter remains open much longer to allow in more light for your exposure.