1 - Where is the wedding?
2 - What time?
3 - Where is the reception?
4 - What time?
Answer those questions and I can help you.
If anything is indoors, you are going to be severely limited by your equipment, mainly lack of flash. Your 1.8 50mm will be okay, you should shoot it wide open whenever you are using it. That means you will have to take care with focusing. For portraits, I would use that 50mm...I think it would get the best results out of what you have. Groups you'll have to use that 18-55mm.
Indoors I use a 70-200mm f/2.8 IS and sometimes I'm still limited and want more light than is available. But I also have a 50mm f/1.4. If I can use flash, I will. Otherwise crank the ISO. On a 30D I would try not to use more than 800ISO, and keep it under that at all times possible. Noise is okay - it can be lessened in post processing. Also if you take a noisy 1600 ISO shot at 8MP and print it on a 4x6, you won't even notice it unless you have really bad chroma noise. Even at 8x10 it won't be nearly as noticeable as it is on a computer screen.
You really will want to shoot RAW in order to fix things later. This will mean you won't get many shots on 2GB cards. I have about 32GB in CF cards. 2 8GB, a couple 4GB and a bunch of 2GB. If it's a long wedding, I'll use a lot of that space. But that's with a 40D which uses more memory.
Expose for the dress as much as possible, as it is usually the brightest thing in your shot. You don't want to lose detail in it. When shooting a wedding I find I use spot metering most, and also center wieghted average. It doesn't really matter though - use the metering mode you are most comfortable with, but you need to understand how it meters and how that will affect your image in various situations.
Figure out who key people are in the family - MOB/FOB, grandparents, MOG/FOG, etc. Watch them when you can throughout the ceremony and reception. If you have two shooters, this is a huge help. One of you can focus on the giving away of the bride by her father - and the other should be concerned with the mother of the bride. You can get great emotion-filled pictures by doing this approach. Also when the vows/rings, etc. are being done - one focus on that and the other on the parents of each, etc. It's nice to have different angles of the same thing too, but the emotion captured by focusing some on family is priceless. Also - when the bride first enters - one of you focus on her, and the other focus on the grooms reaction.
Go to the rehearsal if at all possible. Learn the order of when things happen. The ceremony - even if it is 45 minutes in actual length - will be over in about 3 minutes to you. Your first time it goes VERY quickly and you feel like you don't have time to do anything. This is normal. Welcome to the world of a wedding photog
I recommend shooting on aperture priority, and shoot as wide open as you're comfortable with. With my L lenses, I shoot wide open and don't worry about it, unelss I want a larger DOF for a particular shot. With your lenses, you'll have to worry about image quality with them wide open and I'm not familiar enough with them to recommend a minimum setting.
Hopefully everything is well lit. But be prepared. I once did a wedding in July. It was hot, and the power went out - no A/C, no more interior lighting - wedding went on. I had to change game plans to allow for the huge decrease in available light. Not to mention that it gets miserable very quick inside with no A/C when it's 110° outside.
See if you can rent a flash or borrow one from a friend or something. Bounce flash is best and works very well with a nice white ceiling. Direct flash is bad - you'd really want to diffuse the light. Also if you use a flash mounted on your camera indoors and you turn your camera to a portrait orientation, you will end up with ugly shadows on the walls of the people you're photographing. Ideally you would want a bracket which keeps the flash directly above your lens, but that may not be possible. The reason for the shadows is with the camera above the lens, the light is projected in the direction of the lens, so the shadow is behind the subject. With it turned to the side it's more from the side and you get the shadow to the right/left of the subject depending which way you turn. Also a bracket raises the flash higher. A higher light source, centered over the top of the lens will garner the best results as any resulting shadow will be lower and behind the subject. It's not perfect like a studio could be, but much much better.
Browse some wedding photography sites - look at poses and such and try to remember some to use, etc.
May be able to offer more advice if you post the locations/times. But hopefully this helps some.
I was going to try to find some example stuff, but....I don't have much up I can point to...
On exposing for the dress, I knew I had this shot:
Clicky
The light from the window is somewhat blown out - but it doesn't matter. It could even be blown out more, but the important thing is that dress.
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