Electrical Soldering is the basis of all modern electronics. Although integrated circuits can largely be manufactured without it, they could not be connected to anything else without soldering.
In short, solder is an allow of tin and lead, with a fairly low melting point. It bonds to most metals when melted, making it useful for permanently connecting two pieces of metal.
You will need:
The printed circuit board (PCB) that you wish to attach an electrical component to and the electrical component.
Solder. I used 63/37 rosin core solder. The tube pictured cost about $1 and has 8 feet of solder, enough for almost any project. *WARNING* Acid core solder can damage electrical component.
A soldering iron. These come in many shapes and sizes, but are ultimately, nothing more than a bit of metal, a power source and a heating element.
A wet sponge. Keep some water nearby so you can keep it wet.
Step 1: Place the Component
Printed Circuit Boards have two sides. Typically, only one side has metal printed on it.
Place the component with its leads through the appropriate holes (deciding which ones are appropriate is beyond the scope of this instruction), with the body of the component on the side without metal printing, and the long ends of the leads on the same side as the metal printing. If the component does not stay on its own, bend the leads slightly against the sides of the holes they are in.
Step 2: Turn on Soldering Iron
With the component placed, it is time to get the soldering iron ready for use.
First, be sure it is plugged in and turned on.
*Soldering Irons get very hot. Never touch the tip or store with the tip in contact with a flammable materiel*
Step 3: Tin the Soldering Iron
Once the tip is heated up a bit, tin the tip by applying some solder to it directly. Hold a length of solder, and slowly push it onto the tip until the tip is shiny. The solder should melt and apply itself to the tip quickly.
If you apply enough solder that the tip noticeably changes shape, you have applied too much. Wipe the tip on your damp sponge to get the excess off.
*Every few minutes, you will need to re-tin the tip. Generally, if the tip starts turning a blueish-black color, it is time to re-tin.*
Step 4: Heat the Connection
*Warning* Leaving the soldering iron on a circuit board too long can damage it. Know what you are doing next before attempting this step.
Place the tip of the soldering iron so that it touches both the component's lead, and the metal printing on the circuit board. Hold it there for about 10 seconds and move to the next step.
Step 5: Apply Solder to the Connection
Apply the solder to the opposite side of the lead as the soldering iron. If you have applied the soldering iron right, a tiny amount of solder should immediately cover the metal printing and connect it to the lead. You should use about 1/2 inch of solder per connection.
After the solder is on the connection, remove the soldering iron.
Step 6: Congratulations
You have now soldered a connection! To finish soldering your circuit board, just put components in one at a time and solder them in place. If leads get in the way, they can be cut off just above the solder.