I’ve run demos of my Blades hack at conventions, but never at PAX Unplugged, so not sure how their system may differ or if my advice will be helpful. I’ve run demos at Shut Up and Sit Down Expo, and Terminal City Tabletop Convention.
I tend to have a sign on the table. Just a clear plastic standee no bigger than a piece of paper with the name of the game and something like “SIGN UP NOW” or something to let player’s know I’m looking to host games. You can usually get one at an office supply store. I think PAX might have a system where there will be a sign up table where players can put their names down for games they are interested in, so definitely contact the organizers or post a message in any relevant forum/discord and folks can help you out.
Relevant to that, I usually post something about my game in the relevant forum/discord where it’s appropriate to do so. Its good to give folks as much time as possible to plan their con and may give them the opportunity to sign up early (again, depending on how it works).
I tend to run the same score for the whole convention, usually something that I’m thinking of using as the starting situation in my hack. I do all the mechanical choices on the character sheets before hand (stats, special ability) and let the players come up with a name/look/background/contacts. I also provide lists of suggestions for each of those, as well a few cheat sheets on the core mechanics and what all the standard items and playbooks do, as well as a list of factions.
Your hack may vary, but I found that it’s not worth bothering with vices/downtime stuff/making a crew during a convention one shot. I tend to run games for about 2 hours, and that’s enough time to make characters, introduce each other, and then introduce and execute the score.
Have a plan for how many sessions you want to run and when you’ll run them. Give yourself at least an hour in between in case a session runs late so you’ll have time to stretch, get water, recharge. Try not to overextend yourself!
Have some business cards handy so people can follow progress of the game, if you like.
When in doubt, ask a volunteer! They’re there to help, even if it feels like a mundane thing.
I tend not to front load the rules explanation. I give an overview of the setting, the different playbooks, basic mechanics (you roll pools of d6’s and keep the highest), and then let players make characters. Then I drop the characters into the middle of a scene acquiring a score. Once someone does something risky, I introduce position & effect, stress, and things like assists, pushing, devil’s bargain, etc. Once I give a player a consequence or complication I introduce resistance, harm, clocks, etc.
As far as feedback goes, I tend to mostly spot rules inconsistencies, typos, and small things as the game is played. In my experience players aren’t incredibly well-versed in Forged in the Dark games (usually they’ve heard of Blades, or read it but never played) but they tend to be experienced with other RPGs. So don’t expect real in-depth mechanical analysis. But there tends to be interesting questions that will get you thinking of things you might not have before. “Is there a faction in this world in charge of X? Can I protect my bike from harm? Does the cellphone item come with a power charger? A hands-free device?” Lots of potential corner cases or novel situations that will provide food for thought.
The best part for me is seeing people excited for my game. Even if I didn’t get many design notes, having fun with total strangers playing a thing I made is a uniquely fulfilling experience, and I’m always hyped to get back to the drawing board.
Don’t forget safety tools! I use a YES/NO table where after character creation but before the game begins all the players can list things they absolutely WANT or DO NOT WANT to see in the game. This can range from story tropes and themes the game may explore (organized crime, explosions, car chases,) to broader stuff (bigotry, feelings, detailed violence.) I take the lead by listing at least one thing under NO. Have an X card or something similar at the table so folks can signal when they are uncomfortable. There tends to be unstated social rules when running a game at a con to not trespass into certain things, but it’s better to make it explicit.
Uh… I think that’s it. Hope that helps!