Sound advice from Michael.I would add that its best to do some running and some work on upper body strength in the weeks leading up to the walk.Running will knock you into shape quicker than anything else.

I met a couple of sixteen year old lads on the coast to coast and one made it and the other gave up.Unless you are injured don't let the thought of quitting enter your head.It will be very uncomfortable at times but if you remain positive you will make it.