I already did an instructable on fixing the heel of a shoe. Briefly, glue in a piece of cloth and stitch it in around the top. See here for more det...
Some notes on how I repaired my boots. Includes worn out heels and breaks in the leather along the boundary between the leather upper and the rubber sole.
Step 1: Figure out what needs fixing
The heels were worn out and the leather along the edge of the sole had worn through. (I think this is an indication of poor posture or fit... my feet are probably going to fall off.) The logo also catches on the lacing hooks when I walk.