Now that you collected all the necessary materials, it's time to get started!
1. Design or find a circuit to build!
Circuit design, analog or digital, is fairly involved but lots of fun! I highly recommend a few of the following books to get started:
Design of Analog Filters, Rolf Schaumann
Op-Amp Applications Handbook, Walt Jung (I wouldn't be without this!)
Printed Circuit Boards; Design, Fabrication and Assembl, R.S. Khandpur
You can undoubtedly find all these books at Half.com, Amazon.com, etc. There are also lots of online tutorials covering the basics and lots of circuits already out there ready to try. Manufacturers like Texas Instruments, National Semiconductor, Fairchild, etc. also publish Application Notes that are tremendously helpful (National's Linear Applications Volume 1 is an older, harder to get set of app. notes, but it's a great one to have). When you debug your circuit you'll be glad you learned the important attributes of the part(s) you are using.
Simple NPN boost, drawn in CadSoft EAGLE
2. Design or find a layout of the circuit.
A layout is like a big puzzle. There are infinitely many ways to situate the components of a circuit. A lot of circuits out there have accompanying layouts but I highly recommend trying it out for yourself.
First and foremost, it is extremely important to consider the environment of the PCB. For guitar effects in general, you have to consider how the PCB interacts with the bypass switch, potentiometers, in/ out jacks, battery or adapter jack. If you're not careful, your PCB might not fit with all those bulky parts. If you're careful, clever and select the right components, you can make all these parts mount on the PCB AND the enclosure!
Another critical part of layout is pad size. The pad is a "donut" shaped area of copper where the lead of the component is inserted and soldered. Remember to size the pads according to the component lead size. For guitar effects, resistor and capacitor pads are almost interchangeable. When you begin to deal with semiconductors such as transistors, IC's and diodes, the lead thickness and spacing begins to change depending on the nature of the device, and special care must be taken to get the pins/ leads right. ALL component manufacturers publish datasheets which show all the attributes of the device. Contact the manufacturer directly if you cannot find all the mechanical and electrical characteristics you need.
Below you will find my layout for the simple NPN boost. The idea here is to use a PCB mount potentiometer (pot). When the pot mounts to the enclosure, it will also hold up the PCB inside the enclosure. Notice how all the resistors are in a row for easy placement. Also notice how the "IN" pad is on the bottom. This is in order to mount the foot switch below the pot, so placing the input pad at the bottom of the board like this minimizes the wire needed to reach the switch. NOTE: EAGLE has the option to manually draw traces OR automatically route the traces between components. This is only one powerful feature of layout software.
EAGLE Layout of Booster
All of these are good layout techniques and can be applied in general. Remember, there are seemingly endless ways to layout components. Here I do not address the first and second order affects of component placement for the audio bandwidth, or multi-layer PCBs because it is beyond the scope of this article. Also try to get creative; you don't have to do a boring copyright and "Y."
NOTE: for all of the photo reference steps, I am fabricating a SLO-clone pre-amp, because I need one. This layout was done by JED and you can find it at sloclone.yesterdaysrevolt.com