Establish a budget and stick to it. Quality desks don't have to cost a fortune.
Take measurements of the area you would like the desk to occupy. This will help narrow your search, as there are many options.
Take measurements of all of the critical items that will be placed on your desk--specifically your computer, monitor, printer, scanner and mouse. Nothing is worse than having a computer desk on which your computer won't fit.
Measure the dimensions of your office chair if you already have one. If your chair won't fit under the desk, you will be wasting a lot of your office space.
Consider some of the more high tech options, such as desks with built- in USB hubs, power strips and mounts for flat panel monitors. These are not just convenient, but can make your desk look sharp.
Before purchasing a desk, find a store that has an already assembled unit and test it out. Many factors can't be considered until you actually sit at the desk.