First rule: keep it wrapped tight. Air is the enemy. After you slice off a piece, wrap the cut end in plastic wrap, then put it back in a zip-top bag. Squeeze the air out like you’re giving it a hug.
Second, store it in the coldest part of your fridge, not the door. The door is the warmest spot because you open it all the time. Tuck it in the back, next to the butter or the leftovers.
Third, don’t let it sit out on the counter for hours while you graze. If you’re having a snack plate, only take out what you’ll eat in ten minutes. Put the rest back. This isn’t a charcuterie board at a wedding.