One of the first things to learn is to protect your thigh, the traditional work platform for knappers, with a leather pad. It would also be a good idea to wear safety glasses. I understand Australian aborigines linked as they struck the rock, accomplishing the same end. It takes real skill to fashion a decent tool, but if you are content with a sharp edge, simply bash the rock and sort through the debris until you find a suitable blade. That was the extent of humankind's tool making abilities for quite a few millenia - I personally haven't gotten beyond that stage myself, which is why I usually carry a knife (just as I was typing this, my wife asked me to open a tube of spackling paste - can't be the man of the house without the right tools!)

Modern knappers can replicate just about anything known from antiquity, but the skill set takes time to acquire...