[jpatte]

IMHO this also as a lot to do with setting an appropriate work environment. On a desktop designed for work you should only have links and bookmarks related to your work. A bookmark to Facebook is a constant reminder that there might be something new on Facebook, and it's sole effect is to distract you.

I also noticed that having an appropriate background music is important. In my case I like to listen to Progressive Trance music (mostly ETN.FM Channel 2), and I have hundreds of recorded shows of 1 or 2 hours each. The goal here is to maintain a rhythm : keep going as the music goes on. I never listen to this music when I'm not working, so I ended up naturally associating it with work.

Every time a music show ends, I take a few seconds to look back on what I did during the last hour : did I complete my task ? Do I need a break ? If I feel stuck or tired I stop the music, switch environment to browse Facebook/Mail/HN/whatever, then come back 20 or 30 minutes later. Then I start by "reloading my context", reminding what I was doing and what problems I needed to solve, having a look on my TODO list (paper), and when I feel ready I start the music again and begin coding.