On Mt. Rugged, when you encounter the Buzzard enemy, tell it that your name is Luigi, and you won't have to fight it.
If you can pull off a FP-consuming attack outside of battle (Such as a Spin Jump) and get a First Strike, you will automatically use that attack in battle without using any FP. This also works for Mario's partners' attacks.
While in toad town, from the post office head to the right. Eventualy you will see 3 blue creatures. The one on the left moves its eyes, and the other two dont. Walk in circles around the one with moving eyes to recive more and more hearts!