How to prepare to have a reception in your backyard?

Well, first of all, I think you should to is inform your neighbors of the party, so that they know what's going on, so the "cops won't bust in." lol But obviously wait until a cpl weeks before the party! But I've planned a few big parties before, and the thing to make it absolutely beautiful, is to pick a theme! Whether it's a color, or something you really like, that describes you, and decorate accordingly. There's usually warehouses nearby where you can rent tables and chairs, if you're planning to have food, and you can even rent fabric from the same types of places, for decor and table cloths and such. You may even be able to get a small stage or something for the DJ, if they don't have their own. Obviously your dress plays a huge roll, but you don't have to spend oodles of money to get a beautiful dress. You've got almost a year to plan, but your parents should be helping you plan too. I'm sure they can come up with some good ideas, but there's a TON of party-planning websites, if you just Google Quinceanera themes, etc you'll find all sorts of stuff.