First of all, don't go overboard. We imagine this will be your only wedding - so why not make it special? Special-ing an event takes money. Don't be stingy. Save in other places, if you can, thereby creating energy and resources for the big day. People "back in the day" often used the piggy bank approach to distinguish very special occasions from less special occasions. A coffee a week in the bank, instead of the mouth, won't make that much difference but it will ritualize your intention to have a very special time on your special day. Think "Lay away," again an old fashioned concept but a simultaneous material and spiritual preparation for your wedding. Lay away one purchase a week, like clothes or honeymoon, and you will find it more fun to buy and enjoy, in a slow and steady way.
Secondly, take two years from the engagement till the actual marriage. That could double your time to save and prepare.
Third, consider a double up. Do you know anybody else who is getting married? Many banquet halls have multiple rooms. You could share the rent with someone; you could even have a "double" wedding if your friends and their friends enjoy each other. Likewise many officiants would be glad to "group" the pre marital counseling with convivial people. They would also be glad to do one service at 4 and the other at 5, reducing the preparation of the space and the hiring of musicians and custodians and the like.
Fourth, have a reception at the largest apartment or house a friend has, country or city, or both. Saving your guests travel money by having two receptions could help. Saving gas and travel is a gift to guests and the planet. We often give our apartment in NYC away to people who need a large space. Don't call or write: I am over booked with friends and congregants. But you probably know someone who is house or yard rich. Ask them for a wedding present. Or ask if they could use a little extra cash in exchange for use. Caterers are very good at catering in and are often much less expensive than hotel or restaurants.
Fifth, you could also ask an under employed friend to cater for you. You'd be surprised at how many good cooks there are "out" there. You might even cater the food yourself. I catered my own wedding and would recommend it highly. I even have recipes for 125 in a small bound book! Maybe you have not one friend who could manage the "whole" thing - so ask five. One does the appetizers, the other the main, etc. Just about any good cook knows how to make appetizers for 125 and enjoy it.
Sixth, consider having the sacred ceremony outside or in a church or synagogue or mosque where you attend. Most congregations will give a break to members. And if you don't belong anywhere, find a friend who does. You might let that friend know that you are willing to barter your gift for their space. Do you design web sites? Or a country place some staff member of the congregation could use? Bartering is an under estimated form of economic exchange. Clergy are often quite interested in unusual economic arrangements. Don't be afraid to ask.
While outside services can be tricky, because of that funny way weather has of being itself, they can also be very beautiful and inexpensive. If you keep the group for the actual ceremony small enough, many public parks are ideal and don't even need reservations. Those who do need reservations are booked way in advance. Consider Western Mass Electric's site on the Connecticut River, with Pavilion. $100.00 will get it for you but you need lots of lead-time. Or Washington Square Park in New York. $25.00 under the arch. If you don't want to book or can't book, just show up and say what you have to say to each other. And leave before the cops come.
Small ceremonies have an intimacy that is quite lovely all on its own. And you can still have a larger reception.
Seventh, evaluate all the parts of the wedding and see what you can do yourself. Can you hand write invitations? Can you find a friend with a garden for the flowers? Do you know someone who sings? Plays piano? Bakes a mean cake?
Eighth, consider used clothing. Go on line. Many people have already indulged themselves with one of a kind and never to be worn again clothing for the wedding. Whole "bridal" parties are sometimes available. Size of course is an issue, as is style. But tailors are magicians when it comes to redoing something beautiful into something beautiful that fits you. Recycling clothing is a mitzvah - which means good deed. Imagine the loneliness of a once worn outfit, stuffed away in a plastic bag in a corner of a closet or thrift store. Don't put dry cleaners out of business: they live to freshen the under used items of our wardrobes.
Do you know someone who sews or tailors? Maybe they will do what my sister did for me, for my first wedding, and make you an outfit.
For my son's wedding, I ordered two outfits from Beijing. You don't want to know what they didn't cost me.
Ninth, consider a potluck wedding. Most public halls (but not hotels) will allow you to bring in food. Have an elegant potluck requiring everyone to bring their very best dish in their very best container. You'll be surprised at just how good the food is and how it will make the rubber chicken of yore soon forgotten as the "norm" for wedding fare.
Tenth, I return to the beginning. If you can save on 9 items, you can splurge on the 10th. Don't do anything that puts frugality as the primary goal in the wedding. Let feast be the goal - and let frugality serve that goal. If you really don't have enough money to get married, elope. You can always have the wedding you want later when you can afford it. Think fifth anniversary.