Figure out how much you can afford to spend. You can spend 200 dollars on a smaller, lower-end model and as much as 2,000 on a top-of-the-line blower. Unless you live in an area where several feet of snow several months of the year are the norm, you can find an excellent model in the middle of this range.
Decide whether you want gas or electric. While electric snow blowers are generally less expensive, they also tend to have less power as well. Also, you will have to have access to a power supply and a long enough extension cord to reach the areas you need cleared if you choose an electric blower.
Determine how wide of a clearing path you will need. While your first thought might be that the largest one would be best, consider the fact that you have to be able to handle and store the machine.
Look for controls that you can see clearly and reach and use comfortably, especially with a gloved hand. An emergency stop function control is a necessity.
Decide if you need steerable wheels. This is a feature that will increase the price. However, if you have a winding sidewalk or driveway to clear, it may be well worth the added cost. If you have nothing but straight paths to blow, you probably won't need this extra.