To score an easy 500,000, do a normal run to the bottom of any mountain you feel comfortable on. Try to pull off as many big air grabs as you can while progressing down the slopes. If you have had some practice at the game, you should be able to score 150,000 without to much effort. Once you hit the bottom of the mountain, keep doing Ollie's mixed with grabs and spins. Just keep doing this until you hit the desired score. Don't worry about bailing, as you will be reset to a previous autosave point and your score won't be affected. One thing you must not do is press back or finish your session.