How difficult - and rewarding - do you want this to be? In the first instance, let's say any journey of two miles and under has to be completed on foot, and that includes commuting. Run it if you want, but walking will not only help you shed the pounds, it will also introduce you to some of the hidden delights of your town or city. You don't see much at 30mph - you see everything at two. Do it for a week to start with, and you may just find you catch the walking bug.