I've been using a bright light therapy box between October and March for about 7 years or so. I have a fixture that delivers 10,000 lux at a distance of ~12-18 inches from my face. I use mine for about 30-60 minutes a day, depending on how much time I have and how short the days are. I do it early in the morning, and usually read while basking (one does not stare into the light).
From my research, you should consider intensity of the light as the most important factor--not the color/spectrum. In other words, 10,000 lux is most important, and it matters less if that's white or blue. The evidence for the effectiveness of blue light seems incomplete at this point, whereas the evidence for bright white light is fairly well established.
Contrary to another response, unless something has changed in the last few years, the FDA has NOT approved light therapy as a treatment for SAD. But this doesn't mean it doesn't work. Much like the paleo diet, the actual lived experience of thousands of people might be more relevant than the FDA's questionable authority.
Keep in mind that the benefit from tanning beds or UV light may overlap bright light therapy in some ways, but really you are treating two different things with these two different technologies. Tanning beds and UV radiation can theoretically produce vitamin D, and some people report it improves depression. Bright light therapy boxes filter all UV radiation and will not produce this effect. But they also will not damage your eyes or skin. You can't get a "sunburn" from a light therapy box.
Incidentally, 10,000 lux is about the intensity of full daylight (but not necessarily full, direct sunlight) outside during the summer. If you think it hard to imagine any single fixture producing that much light, you're right. This is why I advise against trying to build your own box unless you're exceptionally clever, or have fancy light metering equipment available that costs more than a purchased light box would. It's just not feasible or cost-effective for most people to build a bright light therapy box capable of producing 10,000 lux with standard off-the-shelf components. The $200 I spent on mine certainly worked out cheaper than 7 years of antidepressant medication, even with insurance.
Finally, distance is important. Most light boxes are designed to deliver 10,000 lux at a distance of 12-18 inches. Let's say your effective dose is 30 minutes. At 24-36 inches, now your dose is 60 minutes. The further you are from the light, the longer you must use it to obtain the dose. So again, intensity is very important unless you have hours a day to spend basking.