1. Purchase shoes from a retailer who specializes in running/walking shoes. Ask the salesperson if they run/walk, since they may have first-hand knowledge of a number of the brands and models.
2. Unless you have been successfully wearing a particular shoe brand/model for a year or more, your salesperson should measure both of your feet with a standard Brannock device, while you are standing with weight distributed equally on both feet. (Successfully means without injury, blistering, abrasion, fasciitis, etc.) However, different brands and styles of shoes size differently, and you may find that you need a different size in different shoes.
3. If you are transitioning from walking to running or are a walker/jogger you should be purchasing running shoes, NOT walking shoes. Also, some walkers like the lighter weight and less solid upper of a running shoe, particularly in warmer weather or climates. Remember, you can walk in running shoes, but CANNOT run in walking shoes. Also note that most shoes designated as cross-trainers are designed primarily for indoor use and side-to-side movement.
4. Your salesperson should ask you relevant questions related to injuries, activity level, mileage, present training schedule, etc. to have a more complete picture of your needs.
5. Your salesperson should watch you walk, without shoes on, from the front and back to determine your footstrike pattern, and observe for over/underpronation, tibial verrum, or other biomechanical conditions which could influence the models of shoes they choose for you to try.
6. Once a shoe has been chosen and tried, the salesperson should feel the shoe on your foot. Especially the length should be checked while you are standing in the shoe; there should be a full thumbs-width of space between the end of your toe and the end of the shoe. For most people this means that they will wear a shoe to run/walk in that is a 1/2 to a whole size larger than their regular street shoe size. This allows for foot swell and motion in the shoe.
7. The salesperson should watch you run/walk in the shoe, again observing from both front and back your foot motion and strike in the shoe.
8. There are many excellent brands and models of running and walking shoes on the market to meet a wide variety of training and biomechanical needs. It is important to have a knowledgeable salesperson to help choose those few that may specifically meet your needs. Good communication with a salesperson is also important - the more information they have, the better they can help you.