P.S. Keep in mind, I was doing a bicycle-themed fashion show. This will not be entirely relevant to a traditional fashion show, but then again, it's also free advice.
Without further ado...
This should be the first focus. I started contacting designers six months before the show. Get started ASAP! In general, you want to get everything started as far in advance as possible because trust me, there's never enough time!
The expo directors had started a basic list of companies to contact, but it was all pretty loose and unorganized. Organization is definitely key, especially if you're going to have multiple people working on the show. So I started a shared google document spreadsheet that had columns for: Company, website, contact name, email, phone number, and communication notes. I also included yes/no boxes for: Participating and Items Donated or on loan. The communication box was absolutely key. Everytime someone had contact (which was almost exclusively me, but it still allowed everyone else to see my progress), I put a note in the communication box with the date, my initials, how I contacted the (phone, email, etc), and general notes. So it'd look like:
01/09/2011 Received email from Nan re: help with SD fashion show (MJ)
01/10/2011 Sent email to Nan re: tips for planning fashion show (MJ)
Once I got some sort of confirmation that a designer was interested, I sent them a contact to sign and fax back. I'd be happy to send you my copy, once I get home from work. To be honest, this was just a precaution- no one ever got to the point that I had to threaten anything legal, but it did help prevent some major issues. [Designer name withheld] sent her clothes only 1 week before the show. The deadline for receiving clothes was 1 month before. There was no way I could get any models in for a fitting, so her clothes never made it on the runway. Her sales rep was pretty annoyed at me, but I had the contract to prove that [designer X] knew the clothes had no guarantee of being featured if they weren't received on time. That avoided a huge issue. Be sure to be clear about your due dates and any other stipulations.
I also sent an packing slip so we knew what we were going to receive. In theory, it was a great idea. In actuality, it was a bit of a mess and I ended up having to do hand counts anyway. Next year, I would definitely create some sort of spreadsheet form that you can email your designers so that you've got everything already in a digital format. This will allow you to create a master inventory list so you don't lose any items. If you're doing a charity raffle like we did, it'll also help you keep track of what is being donated and what is on loan. Finally, you'll be able to create outfits by looking at what you have virtually, rather than trying to go through dozens of packages. By the way, I definitely encourage a raffle to benefit a local non-profit organization. Almost all of the designers donated something and we raised $1,500 for the Bicycle Coalition of Greater Coalition.
One of the places where I could have improved from last year was in the amount of stuff we got. Because we were going to raffle things off, I figured the more the better. While we certainly raised a lot of donations, it created a MESS for creating outfits. I'm not exactly sure how to keep that under control, because not every designer makes both tops and bottoms or you may want to mix and match outfits. Maybe a good guideline is to accept only 2 complete outfits per designer (1 mens, 1 womens). Or be sure that you've got enough bottoms to match the tops and vice versa. If you pick a theme, you'll probably have an easier time creating outfits. Sticking to a color theme (ex: red, black, and white) will also help out. Only accept one size of clothing from designers. Sticking to one size makes everything so much easier.
If you do have items on loan, make sure you've got a decent way to get everything back to them. On that inventory form you send them, be sure to get their return address as well as a way to pay for shipping. Most people will have UPS or Fed Ex accounts. If not, see if they can send you a USPS shipping label or set up a paypal account so they can send you money for you to ship it yourself.
Once you receive clothes (FYI, receiving to your parents house is not always the most convenient!), figure out an organization system. Maybe it's folding and separating by category (jerseys, bibs, socks). Maybe it's getting garment racks so you can see everything at once. Definitely be sure to get garment racks and garment bags for the show itself. We went to Target and got the cheap racks for $10 each. With one per model, it worked out perfectly. Each rack had each outfit detail taped to it so models and helpers could get the models ready quickly and without confusion. I recommend talking to a local college with a fashion design program (or even boutiques if you've got contacts) as they may be able to lend racks or bags.
We decided that we wanted to use real cyclists instead of models. They weren't all perfect sizes, but it gave the show real authenticity and ensured that the clothes actually looked right. Other, unintended bonuses were that it was free and they all brought their friends to the show!
We used a local cycling club to email their membership base looking for models. I also contacted local shops and cycling clubs. When all else failed, I contacted friends. We ended up with 6 models, averaging 2-4 outfits per model. After the show, a couple people said it would have been cool to see more models (even if each model only wore 1-2 outfits), so that's something to think about. As with the designers, I contacted potential models months in advance, knowing that people were going to drop out. There were many flakes, a few creeps, and some people that just weren't really suitable. Get more models than you think you'll need and always have a back up ready.
And there you have it! Maybe not the most professional way to run a show, but keep in mind, this was the first show I ever planned. It was also done on a budget of $250, attracted about 200 people, and ended up being covered by multiple media outlets. I may end up writing a part 3; guidelines for the actual show itself. If anyone would like further specific information, feel free to email me or leave a question in the comments!