The single biggest mistake i ever made building guitars was to build without a fully drawn out, full sized plan. Did that with my first scratch build. Guitar turned out to play and sound great, but there were a lot of asthetic things about the way it went together that could have been much better if I had been working with a plan. If you make a mistake on a part while building to a plan, you can redo. But if you don't know that you're making the mistake until the guitar's already put together, you're pretty much stuck with it. Get a plan. Stick to it. Best advice I can give. I wish I'd listened when others told me.