Tony Hawk: Ride

You should play on casual first to get the hang of the game. Or if you think your good just go straight to confident or even hardcore because the difficulty achievements are stackable.

Message me on Xbox360 LIVE for help or more information.

Play it on hardcore from the start as the difficulty achievements are stackable and its not hard to get to tokyo.
Once you have unlocked the next city, just move straight onto it.
you gain nothing from getting extra points from the earlier cities.