Business cards - obviously, put your name, contact info, and website on it. Maybe use the back to show a nice image of your latest project. It is free promotion and it looks nicer than a boring corporate business card, so people will remember you better. Make sure to bring enough!

Presentation - have a presentation showing projects you did, projects you’re working on and concepts. Maybe some videos if you have them. Put it on both your phone and tablet so you’ll always have it with you. You never know who you’ll bump into!

Demo - make sure you have a WORKING demo with you. Better to show less stuff that’s working than a lot of stuff that doesn’t work. More on ‘the demo’ later.

Mints & deodorant - Always have these close by. Everybody smells after three days of standing at their booth and going to parties till late in the night, there is no shame in that. But there is no reason to leave it like that.

Internet; get a local sim-card or try a Karma hotspot

Prepare your pitch! There are a lot of good articles on Gamasutra about that. (1, 2, 3)

Make appointments beforehand - people will be fully booked by the time they get to a conference so make sure to contact them beforehand and make an appointment.

Bring a hard copy appointment schedule - Better safe than sorry, you don’t want to miss your meeting because your phone was out of juice or internet connection and you didn’t remember what meetings you had.

Research - look up who you are meeting with on LinkedIn, what games did this publisher recently release? Did they win any prizes? Use this knowledge to compliment them, show them you know stuff and impress them. Meeting with publishers is like going on a first date.

Pen & Paper - Old fashioned? Yes, but you won’t have your tablet or laptop available to type stuff because that is showing your demo.

Prepare another pitch! Pitching to press is different from pitching to publishers.

Make appointments beforehand; Try to leave some space between meetings, because they can easily run over.

Have a press kit ready, and always follow-up by sending an e-mail with a link to your press kit. Check presskit() by @tha_rami for an easy to set-up presskit.

Make sure your booth is asshole proof - controllers, monitors, dev kits, pcs, tablets, cables make sure they are all connected to the table. Because people will steal your stuff and you won’t be able to keep an eye on your stuff all the time.

Throat relievers - Strepsils, Anta-flu, Ricola, cough medicine - anything that will help your throat, because you will be doing a lot of talking.

Giveaways - Always have something for people to take. People love free stuff, so it’ll draw them to you. And it gives them something to remember you by when they come home. It can be anything, flyers, candy, buttons, t-shirts, stickers.

Game controls hand-out - a laminated hand-out to give to players waiting in line so they will already know the controls and can start right away when it’s their turn.

Food and drinks - bring water and energy bars or fruit, you’ll get hungry and thirsty and won’t always be able to leave your booth. (Also: food at convention centers is often crap and expensive).

Banner - make something nice that draws attention to your game.

Social media set-up - set-up your Tweetdeck or Hootsuite for the conference by creating lists of speakers and other interesting streams.

T-shirts - print t-shirts with your company or game logo on it. Have more than one if you plan to wear it all week!

Free keys - print business cards and with steam/iOS keys on them so you can give them to that special person.

Money - don’t be cheap, when you talk to someone offer them a drink or pay for lunch. Especially when you want to impress them. Don’t stand there waiting for others to pay.

Don’t try to show everything - show the core. Maybe create content just for the show. A level which is easier or shorter than it would normally be, but does allow a new player to jump right in.

Have a video to show all the other cool stuff that is in the game and leave the players wanting more.

Automatically go to the video when no one is playing.

Don’t explain everything. People just want to have fun, not play a lengthy tutorial for a game they may never buy.

Localize your game for the host country. People will understand your game better and it is polite. Maybe learn to speak some basic words.

Make sure everything works!