There is a lot that goes into preparing for testing a game at Gen Con. Even after you've arranged for the actual games to be played (between First Exposure Playtest Hall, ticketed games, and booth time there was plenty of that), there are lots of other little things to do to help get the word out about the game. Personally, I went with feedback forms, business cards, on-table advertising, and a game banner- and I'll briefly talk about my experiences with each.
The Feather Banner
I had never made a banner like this before, but I knew that I needed something to attract the eyes of people at the First Exposure Playtest Hall in particular. They had mentioned that there would be room for banners of some kind, but by the time I thought of this, I had about two weeks until Gen Con. So I started shopping.
Most sign/banner companies can offer different types of custom banners, with the most common being retractable banners (~$100). Most big games being tested had these, as they're cheap(ish), light, easy to carry (folded), and quickly assembled. The printing is great, and I would definitely recommend it. In my case, I wanted something that would stand out a bit more, so I leaned toward a single-pole banner, or a feather banner.
Feather banners come in a few sizes, but I got a 7' for about $130 from buildasign.com. Additionally, it came in about a week (I paid a bit more for shipping), included a carrying case and a nice platform base, and assembled quickly. The saturation isn't quite as good as I'd hoped, but wasn't bad at all. The website wasn't bad, but it was hard to know if what you uploaded was going to be what you got. In my case, it came looking exactly like it had in the (small) preview. I'm happy enough, and it'll be something that I will continue to take to upcoming conventions when I demo.
Sure, lots of people have business cards for their game. I wanted to have one too, but I wanted to have it stand out a bit as well. I went with Vistaprint.com's Spot Gloss business cards (and used a $27 Groupon to pay for $70 of the order), and was very happy with them. Many sites that do a spot-gloss or spot-uv want an alpha channel to show exactly where you want the gloss, but Vistaprint didn't need it, they did it themselves. They did a good job, too. I got it in 12 calendar days, with no expedited shipping or anything.
Table Advertisement (Teaser)
I already had printable legal-sized decal paper (for some prototype tiles), so designing up a quick image to entice passers-by was quick and attaching it to some cardstock was a cinch. I put it on a fancy photo-frame stand and had a nice collapsible way to call attention to the game (and get the art out there as well!).
I based my feedback forms off of the UnPub form, which I thought covered all the bases but was straightforward and not too long. I had about 30 people fill out forms (only those who completed full games), and making people put into words what they feel is always good. Also, I changed the scale of numbers to be 1-6 (instead of 1-5) because then people can't put anything right in the middle, they need to form an opinion.
Additionally, a surprisingly useful part of the form was actually the "Your Information" section! On their own, people tend to forget to sign up for newsletters / look up info on games they've played, but by putting people actually ON the mailing list means they won't forget. Almost everyone who played wanted to be on the list.