1) Don't buy stuff just because it is cheap. I bought a cheap no name internal card reader and wondered why the sd card would stop writing every 20 seconds. SD card seemed good, card reader was brand new. Long and short of it is, I replaced it with a brand name reader that was twice the price ($18 as opposed to $9) now everything is hunky dory. New one even gave me a microsd slot and usb port.
2) Buying based on looks is no good either. I learned this by buying an aftermarket cpu cooler. The original AMD one was quite loud and cooling was average for video encoding.Went in to PBtech and looked around. Decided on a deepcool beta200ST cos the heatpipes looked pretty. Turns out it has a cheap non-pwm fan and it runs at full speed all the time. Kept things cool, but it sounded like a jet fighter. Went back and bought an equally cheap xilence cpu cooler with no heatpipes, just a big chunk of ally and a good pwm fan, much much quieter. Not quite as good at cooling, but very quiet.
Lessons learned: PWM fans>cheap coolers with pretty heatpipes for quiet cooling
Buy Right>buy cheap
What do you reckon? What lessons have you learned from building PC's?