Paper Mario/Chapter 2: The Mystery of Dry Dry Ruins

Train Troubles
All you need to do is to break the rock in front of the train in toad town. To do this just choose Bombette as your partner and press to get her to blow up near the rock. Then you may catch the train to Mt. Rugged.

Letter Patrol
Once off the train, check the bushes outside. one has an egg (+ 5 HP anytime in battle) every time you exit and re-enter the area. Go up the steps and a parakoopa will bump into you. He will explain that he is missing a letter, and will ask you to help him find it.

This letter is further up our path, and you will need to use Kooper to get it. You really can't miss it. Return the letter to the parakoopa and he will ask you to find two additional letters.
 * First letter

One of them is down a gap where you'll see a broken bridge, and the other you can find through a series of the slides. After finding all of them, take them to Parakarry, and he will ask you if you will keep an eye out for any other letters. Say yes. Parakarry will then join your team. Go back to the broken bridge and head over it. On your way is a tent and some koopas. Give one of the letters you got earlier to the koopa with the mustache and he will give you a star piece. Continue to Dry Dry Outpost.
 * Second and letters

The Mysterious Moustafa
When Mario enters the outpost, he wanders around until you see a mouse thief running from a shop. When you try and enter the shop, it says it's closed. You continue to the next area and see a mouse running from another mouse. You head back to the shop to find it is open again. Buy a Dried Shroom and Dusty Hammer in that order. The shopkeeper will say you must get in touch with Moustafa and to go see him. Go to where you saw the mouse that the shopkeeper visited to find the door will open. Follow the path to a door on top of the roof and enter the door. The mouse will reveal himself as Moustafa and then tell you how to reach the ruins!

Ruin Run
To get to the ruins go north as much as possible as soon as you get out of the town then go west till you get to the area with the one rock in the middle. Use your new item on it and the ruins will come out the sand. Go inside and beat the Pokeys.