If you run Linux, BSD, or any other Free and Open Source system, you know that every time you open your mouth about it in day-to-day life, you usually have to stop and explain what it means. Outside your office or school, there's everyday-type folks who have no idea that such a thing exists, and they'll all have to be taught, one person at a time.
Through the years, I've sought to balance my desire to spread technology freedom everywhere I go with the urge not to make a roaring bore out of myself. For those of you who ask things like, "How do I tell my boss about Linux?" or "How do I recommend a Linux solution to my kid's school?", here's some rough rules of thumb I've carved out over the years which allow the maximum teaching with the minimum amount of pain - for both listener and speaker.
#1. Eliminate computer jargon. I've tried every other way, and it doesn't work. No matter how simply you talk, there will be terms that somebody, somewhere, doesn't understand. Even basic concepts like the CPU, RAM, and the difference between a CD-ROM and a DVD will leave some people far behind. So practice removing as much computer jargon from your discussion of computers as possible. This is a goal to be striven for, without ever being reached. Every computer-specific term you have to use, stop and ask if the listener knows what that means. Make it obvious that you're doing so out of consideration.
#2. Use everyday analogies. We're all familiar with car analogies applied to computer concepts - they're a stand-alone meme on places like Slashdot. To explain why open source is important, I'll say that you wouldn't buy a car with the hood welded shut. To explain the importance of technology freedom, I'll point out that the TV manufacturer doesn't try to control what programs you can watch. To explain the community development model, I'll compare it to a food co-op, a worker's union, or a democratic government.
#3. Appeal to human rights. This never fails to catch the ear of the listener, but I never see anybody online mentioning it. Point it out to the listener: YOU own Linux! Right now! It belongs to you as much as it does anyone else. The same goes for all of GNU-licensed software. You have an inalienable right to control the technology in your life. You have a right to use the hardware that you paid your hard-earned money for, in whatever way you see fit. You have just as much say over what lines of code run on your computer as you do over what ingredients go into your food.
#4. Be even-handed. Lest we stray into "wake up, sheeple!" territory, we should be careful not to be radicals about it. There are other important issues in the world, too. And I don't - and never will - say that FOSS is for everyone. I think healthy eating is good for everyone, too, but I know there are some people who will live on junk food regardless of how many nutritional surveys you read out loud to them.
#5. Demonstrate it. By all means, let people look over your shoulder while you work on your laptop. The most interest I've ever gotten from people is when they see actual FOSS software in action. Just quietly go about your business, and answer the inevitable "Cool! How'd you do that?" questions.
#6. Mention who uses it. There's a dangerous idea floating around out there that Free Software is populated by a community of hippies and flakes, and the hippies and flakes who claim to speak for us will never shut up, so that misconception just has to be tirelessly fought against. Point out places like IBM, Wall Street, Google, Hollywood production studios, and of course the backbone of the Internet. Yes, people in suits and ties with jobs use it; it is part of capitalism! Not outside of it!
#7. Unix-like systems have a heritage to brag about - so brag! The first world-wide web server was a Unix-based system, the first web browser ran on Unix, supercomputers run Unix and often FOSS Unix at that, Linux is embedded in smartphones and PDAs and GPSs. Not just some - but all of the innovation in computers comes from Free and Open-Source Software. And yes, I stand ready to defend that bold pronouncement.
#8. If they're still listening, now you can list the benefits. Here we can cut in the usual spiel delivered online: it's more secure, it's more stable, it's often free-of-charge, etc.
#9. Know when to shut up. Sure, you're passionate about FOSS, but don't let it make you a boring drone. Don't take yourself too seriously, and if the listener shows signs of closing their minds to the concepts you're explaining or seems to not be following it, just let the conversation meander elsewhere, with the assurance that if they want to know more about it later, you'll be happy to explain more. It helps to have your own website to point people to! My average pitch for Linux is down to maybe ten minutes, not allowing for questions and conversational tangents.