Re: soldering
2:30 AM and can't sleep.
If you send me a private message with your email address I'll send you some info/pics,etc. re: soldering guitar parts.
Electronics is my hobby and I've done electronics work on several guitars. I'm not claiming to be an expert, but I've learned a fair amount by working on a variety of guitars.
It is easier to send the info. as attachments than it is to type it all out.
Iwould suggest that you
buy or get an old used/dead potentiometer (pot) to practice on. It would help you more than PCB soldering. Even new, they aren't all that expensive. I put the pot. upside down in a small block of wood with a hole* in it (*for the pot. shaft). This acts as a quick form of stable holder for soldering and makes soldering the ground wire (shield) to the back/underside of the pot much easier.
Make sure that the surfaces being soldered are clean and all oxidation is removed from the metal. The cleaning can be done with emery cloth (someone will disagree here) or very lightly filed/scraped.
Don't use steel wool , especially near pickup magnets.
It is helpful to heat the ends of the wires you intend to solder and run a small amount of solder onto them. Let them cool and then make the joints between the wires, onto the lug, etc.
You might also want to get used to working with
single conductor shielded wire. This type of wire is often used because it helps reduce potential noise problems, and the nice thing is that you always have a source of ground going with the wire you are connecting. Less wires in the control cavity/body of the guitar also.
Wires without shields act as mini antennae.
The lug is the metal terminal extending from the pot. and it has a hole at the end. Put the sink on the lug just below the lug hole where you will be soldering. Try to make a simple "mechanical joint" by putting the wire through the hole, bend it around and crimp it gently. This helps to make the joint stronger and is the proper method. The stability of the joint
should not be totally dependent on the solder.
After soldering, it is suggested to clean the
cooled surfaces with a Q-tip and alcohol (rubbing alcohol...not beer, etc) or a similar type of solvent. This will remove the resin which is apparently corrosive to metal over the long term (probably over hundreds of years or something). Tedious work and maybe not all that essential.
Also, try not to handle lead alloy solder too much and wash your hands after. Especially if you put your hand to your mouth to smoke cigarettes. Although, probably the cigarettes are more of a hazard than the lead

(not a lecture...I smoke)
Heat shrink tubing is sold in various diameters and colors. This stuff is great for putting a layer of insulating material around a wire if needed or for protecting/helping to add extra stability/security to a soldered joint. You just cut it to length, slip it on the wire before you solder( if both ends are going to be soldered), move it out of the way, solder, slide it over the joint and heat it
gently with a cigarette lighter/match.
I slide a piece of heat shrink tubing over the end of the ground/shield part of the wire from the insulated portion of the wire to about 3/16 of an inch from the end of the ground wire and then solder the ground to the back of the pot. This protects the shield from touching a terminal,etc.
Probably overkill.
Using small pieces of color coded heat shrink anywhere on the wires helps to keep you organized as to which wire is going where. This can be a big help. Tubing is a bit expensive, but worth it.
Some of the above will not be appropriate if you work with the pots. attached to the pick guard (e.g., putting the pot. upside down in a holder and some applications will not use shielded wire).
I await the comments of others. We can all learn more from each other.
What type of guitar do you have?