I don't know if fake flowers are cheaper than real ones. Find out names of reliable florists in your area, give them a budget, and ask what they can do with it. If you come in saying you want a certain kind of flower or something, you might unknowingly raise the cost a lot if it's out of season. Let them tell you what gives you the most bang for the buck in your time frame.

The biggest problem you have is the number of people. Whether it's fancy or casual, buffet or plated, no matter what -- feeding 300 people gets very expensive. Liquor, too.

Do NOT try to do the food yourself or have your friends "cater." 300 is just way, way too many for amateurs.

You could avoid serving a full meal -- but ONLY if you carefully avoid meal times, which isn't easy for an hours-long event like a wedding. 2:30 or 3:00 pm until 5:30 or 6:00 might work. Then you could serve as little as just cake and coffee.

Often, a lunch or brunch costs less than a dinner. People drink less, too. But they also don't dance as much or generally get into a party-party mood until after dark, either, if that is important to you.

You can eliminate liquor altogether, or serve just wine or wine and beer, perhaps a signature cocktail.

You're going to need chairs, too, for a wedding at a lake, unless there is a pavilion or something with seating provided.

Skip limousines and favors.

Make your own invitations on a computer and try to keep them so that there is not extra postage.

This will sound counter-intuitive, but the best money-saver we have found was hiring an experienced wedding coordinator right at the beginning of the process. She doesn't make choices for you, she helps you realize your own goals. She has paid for herself every time by steering us to good and reasonably priced vendors, and, even more important, steering us AWAY from ones she knew were unreliable, dishonest, or too pricey. They also know a lot of good tricks that save you a lot of money.

You're going to need someone anyway, with 300 people to wrangle. So get them now, at the planning stage, and ask them about money-saving tips. They know lots.

Good luck!

Ways to save money:
1) Alcohol: if it fits your family's style, go with a dry wedding
2) Flowers/decorations: Ask florist to go with seasonal decorations
3) Timing of wedding: As someone else mentioned, setting wedding at a time when you needn't serve a full dinner.
4) Look up lots of weddings online, focusing on budget weddings, do-it-yourself weddings, and so on; let go of expectations for the expensive, fancy big-city weddings
5) Figure out what's really important to you/your family, and focus on that.

I remember my friend's daughter did her own flowers. She carried a bunch of cala lilies in her hand fresh from a vase. I would prefer to wrap the cut stems with ribbon to avoid getting the sap on the dresses, but it looked pretty. They bought the flowers from the local grocery store's floral department.

Do you know exactly what your budget is? How much money, total, that you will have to spend on this wedding? That's your first step, as you can't really make any plans until you know what you are dealing with.

In addition to the useful information everyone else has posted:

You are going to have to choose between inviting everyone and everything else that goes with the wedding. Every single guest adds to your cost. Which means that every single guest you add to the list lowers the amount of hospitality that you can offer on your budget. I'd take a good, long look at the guest list and see if you can't eliminate 50 people. Cut out plus ones, for instance.

It's just that inviting people and not being able to give them even the minimum of hospitality, which for a wedding would be a place to sit, something to drink (coffee, water) and something to eat (wedding cake) would be ruder than not inviting them at all.

On a limited budget, I'd start by making a list of the things that you and your intended absolutely have to have. You can eliminate flowers altogether if neither of you cares much about them. You don't have to do favors, you don't have to have a cake, or bridesmaids or any of that. You need the two of you, someone to perform the ceremony and, in most states, a witness or two. Start with that and add in only those things that are really important to you, remembering that any guests you invite need something to eat and drink while they are at the reception.

You can also purchase flowers from Sam's Club or Costco, if any of those are near you. A dear friend of mine did that, and and enough for all the personal flowers, table decorations, etc. She did the table arrangements (flowers in a small vase), her mom (I think) did the bouquets and whatnot. All of which can be skipped if you can't afford it. Another friend got plain iced cakes from Costco (two sheet cakes) and used that for her wedding cakes-- another friend decorated them for her. That friend also got married at a lake and the reception was big fun... no alcohol, but picnic food such as sodas, hamburgers, chips, etc. They rented a picnic shelter, it came with a grill, and she hired a friend to do the catering (burgers/dogs/chips/potato salad etc). Cleanup was easy (paper plates etc) and decorations were simple... it was early summer and everything was in bloom. I've also seen weddings w/o cakes at all--- there have been selections of pies, stacks of donuts, etc, all of which worked.

Weddings can be a lot of fun but they can be a lot of work too. A lot of it can be DIY, but you have to also determine what is important to you. Alcohol, no matter how you have it, is going to be VERY expensive. I agree with Camlan, first determine what you absolutely have to have and what you can do away with, both you and your fiance, and go from there. You might be surprised at the all the stuff you really don't want or need after all. All you really need is a bride and a groom and someone to do the marrying, and maybe a witness or two. All the rest is just fluff. Years down the road, your family and friends will just remember that they were part of your day... not that you had an open bar or just served soda and chips.

Oh, and fake flowers are fine for weddings. I carried a bouquet of fake flowers as a bridesmaid 20 years ago, so it's not a new thing.

One other thing I thought I would ask about--what sort of facilities are there at the lake where you want the ceremony/reception? The more stuff you have to bring to the lake, the more expensive it is going to be. If there's already a building there where you can have the ceremony if it rains and that has restrooms, that's good.

But if you have to rent a tent, and porta-potties and chairs and tables and bring in every last spoon and fork and plate--well, that's extra time and/or money. If you hire caterers who can provide it all, that's the easiest and possibly cheapest way to do it. Doing it all yourself is going to involve a lot of time and effort and calling in every last favor from all your friends.

I know a lot of people advise doing the wedding yourself to save money. But with 300 people, I agree with gellchom that it is not going to be possible, even if you have friends willing to help out.

One wedding I attended wasn't very large, maybe 75 people. It was outdoors at the couple's lovely house set deep in the woods. There was only one bathroom in the house, and one bathroom for 75 people is not quite enough when you are all there for 5 or 6 hours. The father of the groom was roasting a pig for the dinner after the wedding, and almost missed the ceremony, because he had to keep a close watch on the cooking.

Outdoor weddings can be lovely, and if that is your dream wedding, then you should have one. But--they are more problematic than indoor weddings, because of the weather. And DIY weddings have problems of their own, because they usually rely on family and close friends of the Happy Couple doing a lot of the work--at a time when they should be celebrating with the Happy Couple.

300 is a huge, huge wedding. The bigger the wedding, the harder it all is, so by all means, get a wedding consultant.

Now, many of the 300 are family and/or close friends? Get reliable ones to help you - maybe finance some of the things you will need, as their wedding gift. Can you give us a ballpark of what the budget is?

I think if you have friends and/or family who are generous enough with their time to OFFER to lend a hand, sharing their talents like baking, craft making, photograpy, etc., that's great. That being said, a request of money to help cover the event, even if it would be considered a gift, seems in very poor taste to me.

I love gellchom's tips!

There are a lot of DIY wedding ideas that are available. You're gonna save lots of money, but you really have to put a lot of time and effort. The flowers poms are my favourite. They're pretty inexpensive and look so chic.

Hire a photographer who's an intern. They might want to include your photos as a part of their portfolio for free. Same thing to the hair and makeup artist or a wedding coordinator.