In "The Acceleration of Addictiveness," Paul Graham posits why things are becoming more addictive, and that if you want to be productive, you need to learn how to deal with or avoid addictive technologies (like TV, for example).
That said, the best way I've found to get into it is a cross between anchors and distraction removal.
The following steps assume you actually enjoy your projects. Your milage may vary.
Step 1: Anchor a song to doing something active, something that gets your adrenaline pumping. My method of choice in this regard is loud DnB music while driving at night on a freeway. Windows down, bass turned up...
Step 2: Never, ever use this song (or those songs) in a work playlist. I explicitly used Immersion by Pendulum for this, and never had it on any coding-related playlist that would come up while I was working.
Step 3: Remove distractions. Coders, don't forget your 15-minute rule-- if you're expecting to get a call, have someone come to your door, whatever, then you may want to wait. Make sure you've got an uninterrupted window of potential productivity. For me personally, if I'm having a hard time of it, I'll drop the screen session with IRC open, close out Gtalk, close out my email, turn off my phone, turn off my second monitor and fullscreen Vim. No distractions.
Step 4: Trigger your anchor. Put the anchored song on, feel the adrenaline start to flow, and get to work.
The more you trigger the anchor, the less effective it's going to be, so you'll want to make sure to keep your triggers up to date, either by continuing to use that song in your active-activities, or by rotating other, newer songs into it.
What technology or websites do you avoid?
How do you deal with addictive technology?