When we keep talking about the benefit of using dual monitors, it seems we have neglected the need for a proper desk.
Not sure you have this feeling or not, sometimes, our desk is not good enough to work with.
I think a proper desk is as important as or more important than an extra monitor.
And I think a proper desk means:
Big space.
Sometimes, the desks are only big enough for the keyboard and the mouse.
Some worse cases I have had are those only wide enough for a small keyboard(those with no keypad) and little room for the mouse to move around. And it is so short that it just put the monitor in front of your face. These desks look perfect compact when you just look at the picture. But when you sit down and try to do something, you will find that it’s completely awful! 
By big, I think it should be at least has room for a keyboard, enough movement space for the mouse, AND space for a notebook or some scratch papers. As to me, I still love using pens to draw or write down something. This helps me a lot in thinking.
What’s more, you should take the monitors into consideration. As the monitors take a lot of space. We always think the the monitors just take as much space as the screen size. But the truth is, we have neglected the monitor stand. It would take a lot space. So you may feel your desk is quite big when you buy it, but after you have put one or two monitors on it, you would find it’s not deep enough or you have little space to put your keyboard and mouse. A solution to this is to use a monitor arm, which will save some space on the desk, as it puts the monitor in the air.
It should be empty under the desk.
So that you can stretch your legs as you want. We may sometimes overlook this. But when we have sitten for some time(over 30 minutes maybe), we would easily get tired if we keep our legs under constriction. It’s entirely not comfortable sitting like that.
Having it empty means you can change your position every 10 minutes and it helps you to focus on your work. Or you would soon find yourselves getting irritable and hard to concentrate.
Proper height.
Height is another factor often got overlooked. Sitting on a high desk makes your arm very tired, especially you types or use the mouse a lot.
The desk in my office is an example of being too high. I have to adjust my chair so that my arms can have a not so bad angle against the desk. But even if I adjust the chair as high as it can, the desk is still too high to reach. What’s worse, with such chair height, I can’t have my feet flat on the ground. So I not only get my arms tired and uncomfortable, my back also suffers a lot.
Not a corner desk(with short sides).
It feels like a corner desk would use the space efficiently. But the truth is, it is not so practical.
I’m talking about those corner desk has not very long sides. Under this case, people seem to always sit at the right angle. And this brings the embarrassment. You would tend to put your arms on the desk. But the angle makes it not close enough to your body. So you have to open your arms to fit the angle, and this make your arms easy to get tired.
If you have found the trick of such desk, you would not sit at the right angle. So you move to the side, and found that there’s little space at each side. This leaves you a lot of space for sundries but little for work. You may even have not enough space for a keyboard and a mouse. :-(
