Walking stick charge attack
Hold [B] button until Bilbo has some circles around him. When you release [B], he will do a rollout attack for a lot of damage.
Trolls' key
The Trolls' Key is found at the bottom of the screen in the room with the trolls, by the wall.
Easy food
Go back and forth through a screen defeating the enemies until you have the desired amount of food.
Defeating the octopus
To kill the octopus in the cave, first weaken him with rocks. Then run up to him and hit him with walking stick or Sting until he goes under. Then back away to the little spot where you entered the room. Avoid the falling rocks. Repeat this until it is dead.