Having problems trimming planes (mainly nose trim)

[MaxGunz]

Slip is when your plane is not pointing where it's going side-to-side. It's what the smiley curve with the ball in it tells you you have, though in a Spit it's a needle down on the lower right of the instrument panel.

Slip makes drag, it slows you down. If you're in slip when you stall, you spin. Slip will throw your shots off to one side.

You fix slip with rudder, hence the term "step on the ball".