How To Advanced....

Make smooth continuous movement

(Using a variable for speed means you only have to change it in one place if you want it to go faster or slower)

Jumping http://wiki.scratch.mit.edu/wiki/Jumping
Shooting Projectiles http://wiki.scratch.mit.edu/wiki/Shooting_Projectiles
Gravity http://wiki.scratch.mit.edu/wiki/Simulating_Gravity
Scrolling http://wiki.scratch.mit.edu/wiki/Scrolling_(sprites)

Use a variable for a timer

(Sometimes you need more than one timer)