One player must keep a map of the expedition's trek, and if two players
make maps the chances for the success of the expedition improve. Graph
paper with 5 or 6 lines to the inch is suggested for underground map
making. A sheet of small size hex grid is usual for outdoors maps. Both
sorts of paper should always be on hand.

Never become concerned if your map is not exact, if it is off 10' here or 20'
there. As long as it gives your party an idea as to where they are and how
to get back, it is serving its purpose. Always make notes on the map to
show danger -- traps, tricks, monsters.