Tilton's Law - solve the first problem first

Quite right.

A client (back when I was a teenage "computer hacker", fixing people's computers for pizza money) had the problem that her computer was unstable. It would shut down at random times. Printing stuff at night only would do it; shortly after printing, the computer would shut down. Also, it would shut down when it was cold, and only restart when the house was warm. And while things would be fine if she was using it, it would turn off if she went off to do other things (e.g. iron her clothes).

Hard to diagnose, but a wild guess: power issue. Lets try swapping out the power supply.

The real first problem: unplugging it. There was a single outlet, with a red/black tree of power strips/extension cords plugged into it. Not just computer equipment, it was also plugged into a space heater, air conditioner, alarm clock, coffee maker, etc.

After plugging all the crap into a different outlet, I unplugged the computer and opened it up. Didn't have a power supply with enough watts. Promised to get back to her in a day or two.

When I called her back, everything was fine. The "teenage hacker" solved her computer problem, stopped her lights from flickering, and made her alarm clock stop turning off whenever she vacuumed.

The problem: 1 socket, about 3000 watts. When it got cold, she turned the space heater on. Computer drained of power, switches off. Print something at night, switch on a 500 watt halogen lamp, computer shuts off.

An interesting counterpoint -- or at least, a tempering perspective -- is the story that made the rounds recently about a consultant who was called in to fix an unstable Linux kernel driver:

The company programmer was slavishly fixing each symptom as it popped up during boot -- that is, each "first problem" he saw. The consultant instead took a look at the code from a holistic perspective, and was able to fix the root cause.

So while sometimes the temporally-first problem is the root cause, sometimes it's just a symptom. Look for the _logically_ first problem which precipitates the symptoms.