1. Read the tech news
Read the news (RSS, social networks, mailing lists). There are many conferences that you can join (some conferences are annual). Unfortunately, the organizers might skip to sent you invitation because you're either too small project without any marketing section or they forgot you for their reasons. You should contact them and ask them to join as community-project. Most conferences have call for papers period, where you can apply for a presentation.
2. Community Meetings
Now that you made the first contact, you should sent an e-mail to your project mailing list, informing them about the conference and asking for an IRC meeting. At the kick off meeting, someone MUST be the coordinator of everything (the tasks are following). Another thing that should be clear is how many members of the community will join. You have to decide early because you can book your trip and accommodation (if the conference is quite big, there won't be any rooms available for you). Travel as a team. If you decide early, you can ask for sponsorship, like openSUSE Travel_Support_Program or GNOME Travel sponsorship (GNOME for smaller events).
3. Ideas for the coordinator
Coordinator doesn't mean that he/she does everything himself/herself. It means that he/she knows everything about the trip and contact the organizers:
* First of all create a wiki page about the event. See some examples at openSUSE or GNOME. Ask members who will join, to write down their name and what materials can bring (even if they'll have their laptops).
* Contact organizers for the booth. How many people will help at the booth. How many plugs do we need. If there's a possibility to provide us with projector or monitors or tv.
* Blog post at community's blog. Re post from members of the community to their personal blogs on different days (we want many people to read it on different days).
* Social media team. Find the conference's facebook and google plus events and join. If they don't have, contact them and ask them if it's OK to create one. Ask members of the community to join the events. Ask members of the community to post everyday something about your project at the social networks event pages (something like: DON'T MISS THE PRESENTATION BY ... AT ...). Don't forget to use a hashtag you want for the specific conference (like #project_is_coming). Remember to use also the "normal" hashtag (example #project). Ask members of the community to retweet you.
* Don't forget to bring a camera. Bring one or more cameras to take pictures or videos. Those pictures will be used for reports (blog posts), upload them to your facebook-google plus groups. Also ask everyone that brought his/her own camera to upload the pictures to your groups or send them directly to you, so you upload them to public place. Don't forget to take the family picture.
4. Swag for the booth
If you're lucky and there's a global project that sponsors your swag, then ask them to send you promo materials. Here comes the coordinator. If the conference is away from your home, then he/she can contact the organizers and the project's marketing materials coordinator to mail them directly to the organizers' address. If you want to keep some promo materials for future events, then you can ask them to mail them to your place. Regarding openSUSE, they can sponsor you to create some promo materials yourself with the openSUSE Travel Support Program.
If your project is small and you don't have enough money to support it, try to have some brochures about it and maybe some promo cd/dvds.
Other promo materials are stickers, posters, T-Shirts, buttons, cubes, caps, plush toys etc.
Here comes the confusion. In my country (Greece), people think the swag is free. On the other hand, they ask us "how the community-project earn money?". Well, personally, I think someone who wants something should "donate" to project. Unfortunately some countries have strict financial rules and it's hard to "sell" something unless you give receipt. Well, I won't analyze this now since it's out of the scope of this post.
5. We're at the conference
Tips to remember:
* Try to wear the same T-Shirt, so everyone will know that you're from the same project and can come talk to you.
* Remember only one person stays behind the table and all the others in front of the table and speak with visitors. It's better to stay 2 of you in front of the desk so it'll be easier for the visitor to talk to you and ask than just one person and wait for the visitor to talk to him (it's psychology). Remember to smile.
Another idea is how to setup your table at the booth. The best solution to have as many visitors as possible is to setup you table behind you, at the wall. That way you'll have free room to stand and talk with visitors. You'll make them to pass you to get some swag as well and either you or the visitor can start talking. Also this setup is just like hug someone and make him feel welcomed (thanks to Jos Poortvliet for this tip).
* Visitors like people from the projects to "goofy" around. Try to play games each other or with friends from other projects. Visitors are very bored of serious guys with suits to try to "sell" them products.
* If a smaller project cannot be present with a booth, you can host them at yours. Let them bring their swag. It'll be cool for visitors to know about their existance and also they'll talk to you about your project.
* Another cool thing you should do (if the room for the booth is enough), you can organize small talks (10-15 mins each). Make a small schedule and print it. Then go to put it on the wall around the venue. Everyone will notice that you'll have short presentations and also your project's logo.
Check out my presentation at openSUSE conference 2012:
* It's prohibited to sit and work at your computer. Visitors aren't interested on projects with someone watching his laptop screen at the booth. You're there for a reason. Talk to people. If there's emergency and you have to chat or reply mails or write code, go to a presentation and do it there. No one will notice.
* Someone should be at the social media. Repost what the official channels post and also do the same if someone from your team is at a presentation and uses his/her social media. That person could be from home (someone didn't attend) since he/she can view online streaming all the presentations. If the person is at the conference, try to upload the pictures right after the photographer took them.
6. Aftermath, afterparty, after after...
You're back. What happened? People MUST know about it. Write a report (even short one) at your community's blog and the wiki page. Use the pictures you took. Send the link to the channels you promoted your party (facebook, google plus, twitter, mailing lists, forums etc) and ask members of your community to repost to their blogs-social media accounts (on a different days).