Gain Access to Special Items
Complete the game's challenge maps to unlock special items. In Cholesteroad and the Massage Parlor, there are challenges that reward you with special items for completion. These items, such as the Daredevil Boots and Heroic Ring, greatly increase your character's stats, making the road ahead far easier.
Level Up
Level up as quickly as possible to face the game's tougher challenges. In "Mario and Luigi: Bowser's Inside Story," your character gains experience for defeating enemies, and this experience is used to increase your attack, defense and special move stats. Find a an area with enemies that are strong -- but not too strong -- to gain experience and level up to handle the game's bigger threats. There is also a special ending to players that manage to get their level above 40 (and another ending for players who finish with a level under 17).
Get the Best Equipment
Get an "A" rating in all challenges and receive two items: the King Shell and the Master Wear. An "A" in the Cholesteroad challenges rewards you with the Master Wear, which adds 25 percent to all special attacks. Completing the Massage Parlor challenges nets you the King Shell, which adds a significant plus-260 to your defense.
Skip the Lumbar Nook.
Speed up drilling into the Lumbar Nook with the following code: "A," "B," "X," "Y," "L," "R," "Y," "X," "B," "A." Normally, as the brothers start digging into the nook, you have to wait five to 10 minutes for an alarm bell to ring, leaving you vulnerable to attack. By pressing the following button sequence, you can skip the wait altogether: "A," "B," "X," "Y," "L," "R," "Y," "X," "B," "A."