This could very well be my auto-biography. Here are a few snippets:
A nerd needs a project because a nerd builds stuff. All the time. Those lulls in the conversation over dinner? That’s the nerd working on his project in his head. It’s unlikely that this project is a nerd’s day job because his opinion regarding his job is, “Been there, done that”.
If you see me daydreaming, that’s what I’m really doing. That’s also how I can spend hours at a bus/train station or airport without doing anything.
Understand your nerd’s relation to the computer. It’s clichéd, but a nerd is defined by his computer, and you need to understand why.
Your nerd has control issues. Your nerd lives in a monospaced typeface world. Whereas everyone else is traipsing around picking dazzling fonts to describe their world, your nerd has carefully selected a monospace typeface, which he avidly uses to manipulate the world deftly via a command line interface while the rest fumble around with a mouse.
These control issues mean your nerd is sensitive to drastic changes in his environment. Think travel. Think job changes. These types of system-redefining events force your nerd to recognize that the world is not always or entirely a knowable place, and until he reconstructs this illusion, he’s going to be frustrated and he’s going to act erratically. I develop an incredibly short fuse during system-redefining events and I’m much more likely to lose it over something trivial and stupid.
Change, eww.
Your nerd has built himself a cave. The Cave is designed to allow your nerd to do his favorite thing, which is working on the project. If you want to understand your nerd, stare long and hard at his Cave. How does he have it arranged? When does he tend to go there? How long does he stay?
Ah the area around my workstation, my mecca.
Your nerd loves toys and puzzles. The joy your nerd finds in his project is one of problem solving and discovery. As each part of the project is completed, your nerd receives an adrenaline rush that we’re going to call The High. Every profession has this — the moment when you’ve moved significantly closer to done. In many jobs, it’s easy to discern when progress is being made: “Look, now we have a door”. But in nerds’ bit-based work, progress is measured mentally and invisibly in code, algorithms, efficiency, and small mental victories that don’t exist in a world of atoms.
Gotta love finding out the rules, and then beating them, breaking bending them.
Nerds are fucking funny. Your nerd spent a lot of his younger life being an outcast because of his strange affinity with the computer. This created a basic bitterness in his psyche that is the foundation for his humor. Now, combine this basic distrust of everything with your nerd’s other natural talents and you’ll realize that he sees humor is another game.
Seen enough of Friends, House & Becker that my humor has heavy dozes of sarcasm.
Your nerd has an amazing appetite for information. Many years ago, I dubbed this behavior NADD, and you should read the article to learn more and to understand what mental muscles your nerd has developed.
How does a nerd watch TV? Probably one of two ways. First, there’s watching TV with you where the two of you sit and watch one show. Then there’s how he watches by himself when he watches three shows at once. It looks insane. You walk into the room and you’re watching your nerd jump between channels every five minutes.
I usually have TV running on in the background, several different active chat programs, people yelling for help while i work.
The skills to interact with other people are there. They just lack a well-defined system.
Anyone who’s ever spoken to me knows this to be true 
*sigh*
The article’s awesome, it’s a long read but well worth it. http://www.randsinrepose.com/archives/2007/11/11/the_nerd_handbook.html
