Setting a huge goal like running a marathon or losing 100 pounds may not be the best way to get fit. These goals can feel overwhelming and cause you to give up when you don't see instant results. Instead, set small, attainable goals that you can gradually incorporate into your lifestyle.
If you're a runner and you run often, you're going to want to replace your running shoes roughly ever 400-500 miles. That may seem like a lot, but if you're running on a regular basis those miles add up quickly. This is to insure that your shoes remain comfortable and aren't causing you blisters or leaving you prone to twisting your ankle.