5. The best quests require a mixture of skills in the party. Find new friends and cultivate ancillary skills. That pesky little hobbit thief may eat you out of house and home, yet sometimes he comes in pretty handy. This is the point of all those tedious "diversity training" exercises from your HR department; perhaps the message would get across better if they talked about the apparently-weak wizard and the bard with those amazing negotiation skills.
Link via Geek Dad, who notes that July is Dungeon Master Appreciation Month