Twitter cofounder and CEO Jack Dorsey got the idea for the real-time service working as a programmer in the dispatch industry as he figured out how to get messages to cabs, ambulances and bike couriers as efficiently as possible.

One day he realized he should have the same service for his friends—notes about "what they're doing," in 140 characters or less—and the idea for Twitter was born.

1. Don't be at your computer all the time.

Instant messaging has always been interesting to me, particularly the away messages you leave for friends. People would leave away messages such as "I'm eating lunch" or "I'm about to go to a movie" but this was limiting because you were always bound to your computer.

I wanted to find some way to get away from that. You should be out doing something and still be able to update your friends and get a sense of what they're doing. Six years ago, the technology just wasn't there to do that. Now, with short message service (SMS), and mobile phones, we can.

Twitter CEO Jack Dorsey

2. The merits of brevity

It's intimidating to figure out what to put on a wall-size canvas. It's much easier to approach a postcard. You can be a little bit more off-the-cuff, more in the moment. It's this quality that makes Twitter different from e-mail or blogs. With e-mail and blogs, you have all this structure, like a subject line. Then, you have this huge area in which to write. All that can be intimidating, especially when you just want to get one message across.

3. Good technology has a narrow focus.

I've always loved systems that do one thing and do it extremely well. The Unix operating system is structured around this philosophy. You have a collection of tiny little tools. They do just one thing, and they do it well. You put these tools together and suddenly, you have an operating system. You have an environment with which you can work. Twitter and tools like it share the same philosophy. If you constrain a technology enough, if you really get it down to an essence, then the potential is unlimited.