Figure out if you prefer a front-loading or a top-loading washer. Consider the advantages and disadvantages of each. For example, while front loaders tend to be more efficient because of their higher spin speed and use of less water and detergent, they're consequently a bit more expensive. They can also can pose more of a safety hazard with small children who can easily crawl into them. Top loaders tend to be noisier but less expensive.
Decide if an energy-efficient washer is something that's important to you. Energy-efficient models -- both top and front loading -- aren't just better for the environment, they can also help save you money on your energy bills. These are usually front-loading units and cost a little more upfront than other washers.
Determine how important the noise level is to you. For example, if your washer is kept in the basement where no one in your household goes unless doing laundry, then a noisy washer might not be an issue. However, if your laundry area is right off of your kitchen or bedroom, you might benefit from a quieter washer.
Consider the size of your space and your loads. The washer you choose needs to comfortably fit in the space you have available. Smaller washers that are designed for closets are available. If you have a little more space to work with, then you need to consider the size of your average load. If you have a large family and your load sizes tend to be a bit larger than usual, opt for a larger washer.