Here is a six-page PDF booklet I created for trail tool maintenance: Maintaining-Trail-Tools
This took some time to research as there is a lot of legend and lore out there in regards to which direction and angle to sharpen tools. I took some of the mystery away, but left enough to let you find your way.
The big picture: keep it keen, and clean
More than you need to need to know about axes, this is a classic: