I'm 24, i mostly work with wood and when i start on the pc i just get measurements that seem to fit. When i'm done, i go to my nrighbour who owns a sawmill and ask what kind of wood he has in stock. I'l change the size of my created pieces on the pc and then i'm pretty much ready to start. Now i know how much wood i need, where to cut it and drill holes and how to connect them. I taught it to myself, so it's not perfect, neither the computer work, nor the wood working but i learn a lot when i'm going at it!