"Assassin's Creed 2" features a main character who uses his environment to sneak up on and dispatch his enemies. You're able to effortlessly scale the walls of buildings when any grips are available, but there are times when you'll need to use the wall as a springboard to jump left or right. The advanced wall jump will let you do this. If your timing is precise, you'll be able to use the walls to jump sideways.
Find any flat wall surface. Most walls in the game are designed for you to be able to climb in some fashion, so this shouldn't be too difficult.
Run straight at the wall. If there is no ledge present, you'll climb it a short distance and drop back down.
Press the "Jump" button while pressing either right or left on the joystick while you're at the apex of your wall run. Everything has to be timed exactly right for this to work. If it was done successfully, you'll jump off of the wall in the direction you were pushing. If something has gone wrong you'll probably jump straight backward and have to try again.