There is only full-on hard work, and away-from-computer restorative time. Nothing in between.
1. When working, disable internet. No browsing around. If you have a long test run or something, usually it's not actually blocking and you can work on something else while it goes, but if it is blocking then just walk away from the computer, get your hands off the machine, do some stretching.
2. No "easing into it". This is a self-indulgence that I can easily fall into, letting myself start slowly in the morning, and before I know it it's close to noon. When you start you just fucking start.
3. If you're tired and can't keep good posture when working, stop working. Go sleep. Work again when you're fresh.
4. Whenever you aren't working, don't do anything that's similar to work. No computer time. Fuck computers, there's nothing good to see on there anyway. Just walk away. Avoid any activity that has your hands in front of your body. Try to spend time with your arms overhead and/or your hands behind your back.
5. When you feel like you need to work but can't really focus, don't substitute shitty work like paying bills or online shopping or fiddling around cleaning up code pointlessly, or whatever that makes you feel like you're doing something productive. You're not. Either fucking get over it and work anyway, or if you really can't then walk away.
6. Be defensive of your good productive time. For me it's first thing in the morning. Lots of forces will try to take this away from you; you need to hold baby, you need to commute to go to the office. No no no, this is the good work time, go work.
7. Never ever work at a laptop. Go to your workstation. If you feel your ergonomics are bad, do not spend one second working in the bad position. Fix it and then continue.
8. Set goals for the day; like "I'm going to get X done" not just "I'm going to work on X for a while" which can easily laze into just poking at X without making much progress.
9. When you decide to stop working for the day, be *done*. No more touching the computer. Don't extend your work hours into your evening with pointless trickles of super-low-productivity work. This is easier if you don't use any portable computing device, so just step away from the computer and that's it.
10. Avoid emotional disturbances. Something like checking email in the morning should be benign, but if there's a 10% chance of it makes you pissed off, that's a big negative because it lingers as a distraction for a while. I've basically stopped reading any news, and I think it's a big life +EV and certainly productivity +EV.