Vievetrick - I recently shot my first wedding in York, ME. Well, I didn't shoot the wedding, they had a kick ass photographer do the real work. My wife was a brides maid and I really didn't have anything else to do the entire weekend (other than partake in quaffing a few beverages).
Some random thoughts and ideas:
-While the entire day is in reality about the bride (makeup, gown fitting, et. al.) try to get some pictures of any groom's metals/ranks/bars/whatever on their own prior to adornment on the groom. Might make for an interesting perspective. I wish I had the opportunity to do this. The official photographer took several shots using a narrow depth of field to focus on the ranks/awards. I can forward the official photographer's site and their proof link leading to a slideshow of his photos for some ideas if interested.
-If in dress whites, make sure the groom is done bleeding after shaving prior to wearing anything white. Trust me on this one.
-If in dress whites, make sure the groom drinks water or something that will not stain the uniform. Didn't have an incident, but a big splotch of Guinness on white is quite obvious.
-Watch overexposure of the bride and groom when using flash. You may need to use bounce or a flash diffuser if you have a hot shoe mounted flash unit.
-The honor guard crossed swords preventing the bride/groom from leaving the ceremony. I've included one picture below:
Otherwise, have fun. There are other suggestions for shooting a wedding in general to also heed (batteries, spare cards, bodies and fast glass, questioning your sanity, et. al.) I'd also defer to anyone with more experience and better information as well.