Various Tips
Hit the rainbow colored bricks any time time that you encounter them as they are far more likely to contain valuable stuff like extra lives and extra hit points.
When you spot an exclamation point sign lying around somewhere that is your cue that you'll encounter something new, like using catapults or pine cones.
To unlock secret stages scroll six spaces to the right from the world select screen. Each 30 pots of gold that you collect unlocks one secret level.