Unlimited Lives
Locate the secret room in level 1 that contains a rope. Climb the rope to the top of the screen and through the ceiling. Collect the extra life, then find the extra life that appears later in the level. After both are collected, intentionally die and repeat this procedure.

The fastest way to kill the level 1 boss
First when you start to fight the level 1 boss, you will see two platforms on each side. If you see the boss walking to the right, jump on the platform when he gets closer. Jump on the next one. Jump off and then hit him. Do this a couple times to kill him.