Full clutch disengagement befire shifting?

I was just talking to my friend about driving a manual and he was telling me that the way I shift is wrong (I fully depress the clutch before I shift gears). He says that I don't have to depress the clutch completely, that if I depress it around 80% (up to the disengagement point), it will be fine for me to shift, w/o damaging the clutch? Is this true? I'm asking, cause he drives an automatic, so his opinion isn't from personal experience (actually, he doesn't know how to drive a manual, he just heard this info from other). Thanks