Instructions
Play through the game until you reach the Ranch.
Talk to Frenchie, who is standing in a nearby alley. Wait for him to instruct you on how to parkour.
Run up to the marked wall and press the onscreen button as you approach it. If timed properly, your character will run up the wall before landing. Repeat this two more times. Frenchie will then ask you to do a wall flip.
Run toward the marked wall and hold the onscreen button as you approach it. Holding the button down while you run up the wall will cause you to flip backward off of it. Repeat this two more times. Frenchie will then ask you to shimmy.
Skate up the marked ramp. Press the onscreen button just as you reach the edge of the ramp. Your character will grab the ledge and balance carefully. Press the button again to let go and complete the trick, impressing Frenchie.