CoD4 PS3 strafe jumping

this might not be the best section, but here I go.

anyone know how to do strafe jumping on CoD4 on the PS3? I checked out some videos of people jumping some stupid distances and jumping onto ledges that seem impossible to get too, anyone know how to do it? I can just about make it work and get onto the ledge outside the window on the backlot and get up to the roof (after about 5 tries), but can't do any of the bigger jumps.