a tweak here, a kernel or a kernel patch there. I'm pretty fussy about the software I install. I avoid non essential daemons, especially things that cause any kind of rise in disk or cpu activity. I make sure everything stays cool. I avoid the power button like the plague.
The very BEST thing I ever did for this box was to remove windoze, which works the hell out of the hard drive and cooling thus avoiding mechanical issues there aside from it being useless bloatware.