@luke
The PDF is great, but I already did a few circuit boards. I do understand soldering etc. The part I was talking about was placed in a single sentence.
> Before you even begin to lay out your PCB, you MUST have a complete and accurate schematic diagram.
A lot of your circuit you can get from reading the datasheets for your components. If you're using an SoC, that datasheet will probably have a circuit diagram you can start with, it depends what you are building.