the secret to corks/bios is always how you "set" the spin. To set a spin, and be able to visualize it easily, lift your arms up parallel with the ground in a sort of circle. (I hope you can understand that). To spin normally you would keep this "circle" parallel with the ground. For bios you want it leaning forward. Therfore making it off-axis. Imagine this circle and spin your upper body on it. This helped me a lot and if I explained it right, you shouldn't have much trouble with it.