1) There are many ways to get tickets. We didn't win our tickets through the free lottery (although we tried, as did several family members on our behalf), and we didn't buy them from a scalper on eBay. Thanks to my friend Beth, we discovered that by donating $200 to become a member of Maryland Public Television, we could get 2 VIP tickets to the Roadshow. Most tickets assign you an arrival time, but the VIP tickets allow you to show up whenever you want between 8 a.m. and 5 p.m. The whole cost of the tickets is tax-deductible, since they are technically free (but given as a "thank you" for membership), and you get to feel virtuous for supporting public TV.
2) If you can, get there early. The appraiser who looked at Steve's sword implied that he would have put it on the list for a TV appearance, but he had already "pitched" a couple of items. It seems that the appraisers want to get on TV just as much as the attendees, amid much competition, so they try to get on the show's radar early in the day.
3) Wear sneakers. Most of the Roadshow experience entails waiting in line. You wait in line until the top of the hour to enter. Then you wait in line to get to check in, where they assign you your appraiser tables with little tickets for each item you bring (each person can bring two items -- and you have to bring at least one item if you want to enter). You then wait in lines for each of your items, at one of the 35-40 appraisal tables organized by category. In all, we were in line for over three hours.
4) Eat a hearty meal first. There happened to be a Starbucks outside the convention center entrance, but it didn't matter, because no food or drink is allowed on the Roadshow set. Luckily, our time there fit squarely between breakfast and lunch, or I might have had a low-blood-sugar freakout.
For the formal FAQ from the show itself, go here.