Ask an experienced x-country pilot to show you how to fold it. So you don't have to wrestle with it in the cockpit. I always cut off the parts I am very unlikely to use
I've been taught two ways of folding maps:
(1) Cut out the bit you need for this particular flight. Throw the rest away. (This is known as the "RAF method".) Draw a new map from stores for tomorrow's flight, the taxpayer is paying after all.
(2) Fold the map. Anyhow, doesn't matter how. Pick an airfield in the middle of what you end up with. Do all your flying from that airfield.