I have apologized in PM for being such a grouchy old meanie. I want to do so publicly as well. The poster was just asking questions, and Kmatfish was right to help, no questions asked. I was wrong to have a vent.
Kmatfish is right in every regard. Use your fastest lens as even in the daytime, a church can get pretty darn dark. Be sure to ask the officiant if he has any rules, unless you are going to be shooting from the pews. Most officiants insist on no flash, and that's why you want the fast lens. If shooting from the pews, get up fairly close so you can go tight, as the hired gun in the back might not be able to depending on the size of the chapel. I've only been allowed flash once, and that was during procession recession, so be prepared to shoot without it.
Shoot in apeture mode, at the smallest apeture you can go, which I think you said was 1.8. You might could even do 2. or 2.8 depending on the light.
Another great point he had was to shoot different things. If you do the same shots as the hired gun, most likely he or she will be flaming you in DWF the next day. Ask questions of the main photog, but make sure he or she is in a lull moment. It can get pretty hairy for us at the church. A good thing to do, and what a lot of second shooters do, is concentrate on all the little details. You'll find tons of them at a wedding. Photograph everything the couple might have purchased or made. Play with dofs. On details, the lowest dof is almost always the correct choice. Look for angles. For instance, find the unity candle and shoot it low, where a stained glass might be in the shot.
Once you get to the reception, put a stofen on the flash and point it backwards. Switch your camera to Manual mode at a 250 shutter speed and just have fun. Be sure to try to stay on a 45 degree angle to the main photographer. Not too close, but not in the shot either. Play with the cake. Keep an eye out for the emotions, which will run rampant. Again, use your 50, or you won't be able to get a shot off, because believe it or not, the reception lighting is often worse than the ceremony lighting.
If you are lucky, you will have a DJ with a light system. I have a ton of fun with these. Compose on the flashing light (red, pink or blue-avoid white or yellow), recomose on the subject and fire. This will give you a great action shot with a big burst of colorful light.
During the leave, find a spot to the LEFT of the hired gun, but not too close. If you can find a high area, that would be cool.
Anyhoo, I hope some of this helps, and I'm sorry again for being such a big grouchy head.
Hugs,
Cindy