Often neglected is the importance of your physical surroundings when you code, yet I think your environment can have more of an impact on your productivity than a fully tooled IDE. Do you like the lights full glare, half, or off altogether? Do you hate it when the office is cold? Do you use a space heater? Does your chair recline? Is your keyboard the natural type or are you standard layout junkie? Do you absolutely have to have dual monitors? Do you listen to music while you code? What kind?
Personally I like it dark. No lights on at all would be ideal, but I compromise with my office mate by turning on one small light :). Warm -- preferably in the upper 70s or as high as 80. If it won't get that warm I wear a jacket almost all the time (at the moment there's snow on the ground outside, so I'm quite out of my element!). I only use standard layout keyboards (although I'm trying out a mildly natural layout right now, with some humorous results). I prefer to lean back in my chair, pushing my chair as far under the table as it can go so my chest is up against the desk. This lets me rest my arms on the table easily. I definitely notice an increase in my ability to stay focused on the task at hand if I'm listening to music with head phones on, usually some form of ambient or techno. Unfortunately I always forget to put my headphones back on after taking a phone call, guest, or trip to the restroom. Duel monitors aren't a must, but they sure help a lot. I use a dark background color scheme in Visual Studio, it's much easier on my eyes. Because I sit so far into my desk, the monitor is set a ways back.
It's amazing how much easier it is to focus when most of my preferences are in perfect tune with one another. But one person's preferences are another's torture.
What are your preferences?