Bias handles in their free state can be either a blessing or a nightmare. There are times where being able to adjust the magnitude, alpha and gama all at once can be very useful, but most of the time I find it much easier to work with one aspect of the bias handles at a time. There are hotkey's that you can hold to lock out certain aspects of the bias handles, but for the most part I find my self adjusting the bias handles by simply dragging on the attribute I want to change in the properties panel.
Magnitude adjusts the weight of a specific handle
Gama most of the time adjusts the spline in and out agains the surface
Alpha most of the time adjusts the spline back and forth along the plane of the surface
There are times when alpha and gama can reverse their roles, but most of the time this only happens around 5 point patches
If you want to see what these attributes do better, lathe your self a sphere, select a point, and start playing with each of the values. It will become a lot clearer what they do, and they shouldn't be feared like the black plague