You might also want to sniff certain components.. This sounds silly, but you CAN smell burning on a burnt out component. Smell your MoBo in various places, and all your cards / components.
Very good point. If the malfunction occurs inside an electrical component, obviously you won't see anything. But you can sometimes see burned out resistors/capacitors etc.. on the circuit board as well..
You'll be looking for dark brown to black coloration on the board. It can look like a small fire/explosion occured, Sometimes just a spot on the board darkens in color, and sometimes even see this appear as dark brown/black dry "puddles" on the solder side of the board. The puddles are darkend flux, used in the soldering process. And rarely, but it does happen, is you will see electrical components DESOLDER themselves from the board, creating small silver balls inside your equipment or on the circuit board, which leaves a component pin not making any connection.
A good solder joint will look like a tiny silver mountain/hill with a gentle slope, with a tiny point at the tip.
IMPORTANT NOTES: When handling electrical equipment, IE: your hands make contact with circuitry inside, you MUST wear a GROUND STRAP, OR TOUCH A METAL OBJECT TO REMOVE STATIC DISCHARGE. Avoid carpeting/flooring that will build up static. Avoid humid areas.
AVOID touching solder points with your fingers (This can short a connection, or can make a connection). Capacitors can store a charge for a long period of time (sometimes minutes, sometimes YEARS). Capacitors look like little batteries, and will sometimes look like large pills/vitamins in older electronics. Capacitors CAN kill you. It only takes 1/10th of an AMP to kill a human being.
Common household circuits are 15, and 20 amps. Which can potentially kill 150-200 human beings. Use safety, and extreme caution when handling electrical equipment. You can easily damage yourself, your equipment, or others around you.