The fight might be over the guest list, who stands where, the colors of the wedding, what happened on the honeymoon, or even the in-laws. The first thing to remember is that you each are different and you each have a different view of what is going on. Back away for a minute and listen to each other without interrupting. If need be go to another room, go outside do something. When you meet again have a good reason for your point, come to an understanding and agree. Some things that people don't understand is that it is ok the agree to disagree. It is still a win-win situtation. Work it out before the weddding or work it out before a divorce.
You may find someone that is not a part of the party to sit and listen to what you both have to say and be impartial Come up with suggestions to make it work, write them down, go with what you both have agreed on.
Most of all enjoy life and don't let the little things separate you.
Blessings on your day.