Music that puts your brain into flow[1] - I have a special playlist for that. The Tron soundtrack fits well if you omit the parts of Jeff Bridges talking - background talk is extremely distracting.
Exit email - I check it mornings, lunch and half an hour before stopping work. Omit mornings if you're already motivated to get right into your actual work.
Get a quiet, distraction-free environment. If you don't have an office with a door, claim a meeting room. Put a "don't disturb or I'll cut you" sign on the door. Be prepared to cut invaders until they learn. Tell them to email you and expect to wait half a day for a response. Tell your manager how important it is not to be disturbed and get them on your side (assuming they want you to get stuff done, that shouldn't be too hard), so they protect you from invaders instead of being one. Working from home can work, if you don't have family or other distractions around.
Staying late works, but your brain is probably not at it's best performance near the end of a working day.
Keep a to-do list[2] and go over it once a day, prioritising important tasks and breaking items that are too complex ("write LDAP authentication plugin") down into simpler steps ("find python module for LDAP support", "figure out our LDAp server's hostname", ...).
Take breaks. If you're stumped on something, go take a quick break (I make myself a cup of tea), but keep the problem in mind and don't interact with others during your break if possible. You will sometimes find that a great solution comes to you without thinking about it (because the non-dominant part of your brain will submit solutions).[3]
If you're really stumped, worked on another part of the problem and come back later. You might come up with a good solution while sleeping on it or working on the other part.
Phones are an evil relic of the past, when people thought they had a right to intrude on other peoples time whenever they pleased. Turn it off. If you're writing code for a living, only your boss and your SO should have your phone number and they should damn well know to not use it unless there's a real emergency that requires your immediate attention.
And last but not least: Make sure you're working on something you WANT to work on. Otherwise you will procrastinate, no matter the consequences. If you are working on something you don't give a shit about, or worse, you actively hate your work, think about why and go fix it.
[1] http://en.wikipedia.org/wiki/Flow_(psychology)
[2] http://culturedcode.com/things/ (Mac) or http://www.rememberthemilk.com/ (Web) are nice
[3] can't find this article: How the classic concept of brain hemispheres is wrong, but we still have dominant and subordinate "halves" and how most techies are logical dominated and the non-dominant "half" will only get a word in if the dominant part shuts up for a moment (which is why you have good ideas whilst going for a walk, taking a shower or making a cup of tea)