Turn on perfect balance cheat and head to the Street Skate Ventura level. Go to the pool which is right behind the place where you start. If you grind the edge of the pool you will never fall off or stop the grind, even when time expires. You will be able to rack up as many points as you want. Jump and land during your grind to double, triple, or even quadruple the value of the grind. Don't forget to hold your balance!