You should buy new running shoes every 300 miles.
To keep track of your mileage, write the date of purchase on the shoes and only wear these shoes for running. If you run roughly the same distance each week, or increase mileage at a steady rate (as mentioned in tip #2) then you will know how many miles are on your shoes at any given point in time. Once you hit 300 miles, buy new running shoes.
Increase mileage by 10% maximum each week. (total miles)
Total miles per week includes time walking, running or standing. As a rule of thumb, standing for 30 minutes is the same as running one mile and walking 20 minutes is equivalent to one mile.
Log your miles in a notebook.
This does not need to be a fancy journal - you can pick up a small lined spiral notebook at the drugstore. If you log your miles - including time standing and walking - you will have a much more accurate picture of your total mileage. Also, you will be less likely to increase mileage too rapidly (tip #2) or wear shoes beyond their lifespan. (tip #1)
Wear cushioned everyday shoes
Everyday shoes are those that you wear for work or around the house.
Shoes you wear during the day make a difference. Cushion is important, so when choosing an everyday shoe consider brands like Clark, Mephisto, Keen, Timberland, Merrell, Rockport, and Ecco.
Running shoes as an everyday shoe
If you work in a casual environment, or have a job as a fitness instructor or gym teacher, you may want to wear a running shoe as your everyday shoe. This is fine, as long as you replace these shoes every 3 months. Be sure that this everyday shoe is different from the shoes you wear while running.
Starting a running routine
If you have never run before, start by running 2 miles 2-3 times per week. Then, you can increase your mileage by 10% each week if desired.
If you are on a sports team, remember that 15 minutes of sports practice is roughly the equivalent of running one mile. When calculating your weekly mileage, be sure to add any sports practices to your total.