Okay, wedding advice for new photographers:
1. Talk with the bride (and bride's mom) beforehand. Be clear about what specific shots they expect and what final product they want. If you give them a flash drive with a bunch of RAW files and they go "but where's the printed photo album????" then you've just ruined a friendship forever. Be totally clear on expectations and the only way to do that is by managing them upfront. Does she want photos of the cake without any people? Of the table settings? Of random quests without the B&G? Especially in terms of what they expect in return...prints, electronic files, photos they can duplicate and give out at will, wedding books and portfolios...get clear on this.
2. Think through how you're going to shoot this wedding. There are a range of different approaches...the photojournalist (like you're shooting a story), or one that focuses on the traditional iconic photos (bride and groom cutting the cake, bride taking off garter, etc.), one that is more artistic (less about the traditional photos and more about photos that capture the feel and memories of the event....such as an empty church with rose petals down the aisle fading off into a blur. Again, this is about managing expectations.
3. Put together a shot sequence checklist, put it on a clipboard and velcro it to your thigh or hang it from your tripod. If you want to shoot a portrait of B&G with Aunt Gussie and Uncle Fred, make sure it's on the list. You'll be shocked how many "required" photos there are for most weddings.
4. Rent/borrow a second body. Being a wedding photographer is like being a photojournalist in at least one regard--you don't get to do "do-overs." If your battery runs dry, you sweat on your lens, your SD card is full or some other problem develops, you can't yell out during the ceremony "HOLD IT--I'VE GOT TO GO TO MY CAR AND FIX THIS--BE BACK IN 5 MINUTES!" And yet there are simply some shots you're not allowed to miss. So you really should have 2 bodies. I know a few wedding photographers who make a living with just one body. But most I know either carry 2 bodies OR they have an assistant (to provide logistical support and also a second camera during the ceremony). Related to this--I'd get there early the day of the wedding, do some shooting and then load the files to your laptop and check them out. You're not a vet with 200 weddings to your name. You don't want to shoot the wedding and then discover that you had done something stupid like fail to correct exposure compensation from your last shoot or had accidentally set autofocus on a different point. Shoot something early and check it. B/c once the wedding starts, you won't have that chance.
5. Visit the site before the wedding. No, not an hour before. Get there on a day that isn't the wedding and during the same time of day as the ceremony. It would be ideal to walk it through with the wedding planner. If he/she is any good, she'll be able to help you visualize the setting. Look for likely hot spots or areas that will produce a lot of glare or mottling on faces b/c of uneven light (often happens with an outdoor gazebo). You want to check for light sources (what kind of artificial and natural light do you have?), where to set up to get the best shots for the ceremony, and also where you can set up your "portrait studio." Let's face it--you're going to take shots of the B&G posing, B&G with both sets of parents, each set of family, with young kids, maids, best man. And some Moms will say "hey--let's use this as an opportunity to get portraits of all family members" so you'll be asked to shoot Uncle Jim and Aunt Maude with their kids and then Aunt Jilly with her date and so on. You want to find a space that works (out of the crowd flow) where you can get up (and you'll need a fill flash at minimum if this is outside in bright weather and almost certainly a soft box or umbrella with speed light if it's indoors, maybe two lights if it's a typical church with a basement reception hall or a hotel with fluorescent lighting) where you can hustle people in, get them to pose, shoot and then move on to the next portrait grouping. HINT: if you don't have an assistant, enlist the aid of the best man or maid of honor to help you here...someone who will dragoon people and say "okay--we need the bride's parents--Jim and June--get your butts over here!" so you can focus on shooting.
6. Put together a checklist of everything you need to bring to the wedding. I know--sounds idiotic. But you're not a veteran wedding shooter and a checklist means you won't forget key stuff (like a backup battery or extra SD card or microfiber cloth).
7. Think through what you're going to wear. Personally (for a woman), I just pants and black clothing (or dark clothing). Why? If it's good weather and outside, you may end up laying down on the grass at some points. Or laying down on the floor. You may get drinks spilled on you. Or b/c you're focused on possible shots, you sit down on a plate with some cake on it. And you don't have time to take 10 minutes to go into a bathroom and clean up. Wear clothing that hides dust, grass stains, and food spills.
8. I think I recall you posting that you don't do much with speed lights. You're really going to need one (maybe two depending upon the portrait station) to shoot a wedding. Even if it's mounted on camera and you bounce it off the ceiling.