1. Take BreaksThe best way to prevent eye strain is to not use them as much. With your eyes that may be difficult to do. Luckily your eyes use more than one set of muscles. That means you can relax one set while using another.
Shift your focus from near to far on a regular basis. Shift focus from up close to at least 20 feet away.
If you are at your computer look out the window for a minute. If you are driving check your speedometer every so often.
2. Reduce GlareReducing glare will dramatically reduce the strain on your eyes. Use non-reflective interfaces whenever possible. Like reading from paper instead of a computer screen. When you have to use a screen make sure it is at a 90 degree angle from any direct light source.
Use indirect or reflective lighting whenever possible.
Try switching your monitor or TV to a flat screen technology. They are not as reflective.
Use anti-glare technology. Use an anti-glare filter on monitors. Use anti-glare glasses when driving (especially at night) or working in general.
3. Adjust ContrastEnsure there is good contrast with what you are looking at but reduce contrast for periphery. More contrast makes edges more discernible so the eyes don't have to focus as much. But too much contrast with the surrounding area will cause strain through your peripheral vision.
Keep overall lighting levels at a moderate level so there is good contrast around you but glare does not become a problem. Use task lighting to aid eyesight at specific tasks.
Adjust the contrast setting on monitors and screens to the best effect.
Use glasses or sunglasses with polarized lenses as they increase contrast and cut down on glare.
4. Adjust ColorUse full spectrum lighting. Lighting, like sunlight, that covers the visual spectrum makes things easier to see.
Adjust the color setting on monitors and screens. Some even allow you to adjust the color temperature.
Use a combination of florescent and incandescent lighting. Use full spectrum florescent bulbs. GE makes a bulb called "Reveal" that improves the color spectrum of incandescent bulbs dramatically.
Full spectrum lighting has the added benefit of fighting off the "winter blues.'