On the rivet levels (where you make Donkey Kong fall), position yourself very close to DK. Each time you jump up you'll get 100 points. If you're going for a high score, this is not really worth it because as you're taunting DK, the bonus time counter keeps on dropping.

On the rivet levels, if you find yourself trapped by fireballs at the edge of the screen, jump off the edge of the level. Mario will "bounce back" after a short delay, during which the fireball may have moved elsewhere.