When i got my first knife i must have been about 7 or 8 years old. We (me and my cousin) got them from my grandfather and my great uncle. If i remember it correctly, they gave us an axe, knives, saw and chisels and and order to do something out of piles of wood, maybe a panzer (they must have been very pissed off because we kept asking them this and that all of the time).
Howevers, both these dudes were very handy with tools and knives, and since both of them were vets (my grandfather from Finnish army and my great uncle from German Viking SS) they had probably used knives other than woodworking too, but that is the thing we never will find out as they are both dead, and they never told anything about war. Once when my great uncle was drunk i asked about how does it feel to be a war hero, and he said that all war heroes are dead. Nowadays i can understand his statement.
Anyways, back to topic. i was taught that the length of the blade should never exceed the width of your palm. Otherwise you can't control the blade. Lesson #2 was that stabbing is a misuse of a knife whatever the purpose. That's why the finger guard is for pussies. Lesson #3 was to never keep your free hand in front of the blade. I think all of these rules were correct.