The biggest impact on the cost of your wedding is the number of people that attend your wedding. More guests mean more invitations, larger venue, more food and more drinks.
Most caterers and venues charge on a per-head basis so the size of the guest list makes a big difference. Start your guest list with a fantasy list – include any and everyone you’d like to invite if money was not an option. Then come back to the real world and see how your list compares to the size of your venue and budget. Be sure to ask all persons involved to provide names for the list - your parents will have their own ideas of who should be on this list. When including suggestions from others, ask them to rank them by level of importance (Aunt Susie #1, co-worker from three jobs ago, #463).
Next, organize them into two categories – the “A” list and “B” list. The A list are the must-have’s - immediate family, favorite Uncle, etc. The B list while still important, you could skip over if needed such as a close co-worker. It is a good rule of thumb to invite approximately 10-20% more than your target number as that is the average of how many will decline. If most guests are traveling from out of state, that number can climb as high as 50%. Start by mailing all invitations to the A list first, and for every regret, mail an invitation on the B list. Just be careful not to make it obvious that you have two lists with large gaps of time in between.

