The art of getting and staying in good shape is one that unfortunately escapes many of us. The good news is that you can bypass the countless and often confusing set of variables surrounding success or failure with regard to fitness by simply putting one foot in front of the other and walking or running your way to a healthy lifestyle.
The key is to start out slow and work your way up to higher levels of training. If you are a steadfast "do-it-yourselfer," that is OK, too. Just use what is called the Away and Back technique. This simply entails easing into exercise by walking or running from one point for a specific amount of time and back in the same amount of time. For example, power walking 10 minutes away from your house, then turning around and walking 10 minutes back. You've got to finish the workout because you've got to get home!
Using minutes rather than miles is a smarter way to start and you will be surprised at how fast your body will adjust if you start by walking or running for short amounts of time, slowly increasing the amount of time you exercise each week. This allows your body (i.e. muscles, joints, tendons and ligaments) to follow a natural progression to higher training levels with far less risk of injury than with a "Weekend Warrior" who tries to do too much too soon. Once you can briskly walk or run for 30 or more minutes, you can move on to using miles to chart your sessions.