Ergonomics is always really important, no matter what kind of work hours you put in. Here's a few tips that'll help you get a better work environment.
Use external gear when on a laptop
If you're using a laptop a lot, external gear is really important. With external gear, I mean a monitor, a keyboard and a mouse.
It's really bad sitting in front of a laptop day in day out, not only because of ergonomics but also because we're human and not used to work the way we do with laptops. Using external gear will make you feel better and it'll surely improve your body position when working.
Also - make sure you spend money on great external gear - it's an investment that's worth more than you think.
Get a great arm chair
An arm chair is one of the best investments that can be made. A good chair will be more useful than you think.
It's important to get an arm chair with adjustable seat, back and arm rests. Make sure the chair feels comfortable and adjust it to your measures to get the best possible out of the chair.
If you have to raise your chair so that your feet are dangling - get a footrest.
Be aware of your weaknesses and do something about them
Do you know you tend to not sit with a straight back when sitting in front of the computer?
Do you know the monitor you're staring at hour after hour won't do you any good?
Do you work with few light sources?
Do something about it!
Improve your position by thinking at how you sit in front of the computer. Sit up straight!
Get a new monitor and adjust brightness, contrast and sharpness. A good tip is to turn down the brightness to around 50 %, it'll save your eyes and save you some headache.
If you're a developer, use a dark theme with your favourite developer IDE (eg Visual Studio, Eclipse etc).
And one very important thing - make sure you've got enough light when working. Probably a desk lamp.
Pause from work
Every now and then, take a pause from work. Just leave the computer for two minutes and do something else. Do this a couple of times during the day. It's way better taking many short breaks than a long one.