Quiet, access to reference resources and a laptop. (Eclipse also helps make it easier.)
A professional programmer gradually learns the art of ignoring / not allowing external distractions to adversely affect their working. But the secret to productive development is focus. Whatever detracts from getting "into the zone" will prevent progress. Environments where frequent interruptions are part of the culture must be avoided at all costs.
The same thing that anyone needs in order to concentrate: quiet and no disturbances.
pair programming or earphones with good music, no telephone, no mail.
I guess it differs from people to people. For me, the very quiet and serene atmosphere does not work. I am at my best with music and when my energies are the heighest
Just not to be interrupted, really, don't really need quiet, just not to be bothered. I think none programmers just don't understand that once you are in the zone, it's some times hard to get back out of it, so, they come over to your desk and just start asking questions when you are like 20 levels into a train of thought, you have to wind back out of that, discuss what they want, then get your self 20 levels back in again. It can be quite frustrating some days :S
No magic, Silence and peace
good keyboard, and leave me alone.
I recently invested in a pair of really good headphones. These block out any external noise. I'm set.
I generally need my seat to be at a certain height (so my legs aren't cramped when they hit the floor, and my shoulders aren't cramped when I rest my forearms on the desk), and some music on my headphones enough to keep the hyperactive part of me occupied. Depending on the difficulty of the problem that I'm trying to solve, The music ranges from fast, heavy base, techno, etc (easy problems) to Yanni, Beethoven, Instrumental, etc (tougher problems) or just the headphones with no music, to block out ambient noise (very difficult problems)
I need quiet, and a long period of time without interruption. Preferably control over lighting and heating, as well as the freedom to be able to take a break and recharge.