The biggest mistake is not setting a realistic one. Too many couples set a budget without having any idea what wedding related things can cost.
Before you even start on your wedding budget, do your research. Think loosely about the type of wedding you want to have and what things are most important to both of you. Notice I said both of you; not your Mom and Dad, or your Aunt Rita or the lady at work, just the two of you.
Now do your research. Make a few calls and get pricing. I am willing to bet that you have never hired a DJ, professional photographer or catering hall before now. Chances are good that you have no real basis to judge what these services will cost. So before you start your budget go find out what the goods and services that you want really cost.
Now you have a way to plan your wedding and more importantly, your wedding budget with the knowledge you need.
The second biggest mistake is to overspend on the things that aren’t the most important to you. Every couple is different. Don’t structure your budget using someone else’s priorities. This is your wedding, spend on those things that matter to you and reduce or eliminate those things that don’t. Listen to your inner voice, not everyone else’s voice.
If a close family member is insisting that your wedding won’t be complete without XYZ and it isn’t in your priority list or your budget, consider asking them to pay for it. For instance if one of your parents has their heart set on an open bar and you are happy with the wine and beer that fits in your budget, suggest that they foot the bill for the bar. My point is stand firm on what you have budgeted.
Last but not least, don’t get locked in to anything before you have a complete plan and budget. Planning a wedding is a very emotional time, it is easy to get swept up in the moment and commit to something before you have carefully considered the effect it may have on the other parts of your plans. Yes, the very best venues and photographers fill up quickly but that is no reason to sign on the dotted line without taking at least a day to give it full consideration.
Above all else, remember this is but one day in your wonderful life together. Being smart when you plan it will get you off on the right foot.