Paper Mario: The Thousand-Year Door Tips

Very easy money
When you go to keelhaul key, go left out of the village. Go up as far as you can. A mole will pop up out of the ground. Hit the mole with the hammer and you will recieve a whacka-bump. Exit the area, then hit him again. Repeat this untill your inventory is full. When it is, go to the shop and sell them. You will recieve 50 coins for each whacka-bump. This will only work a certain number of times.