Simple things like not putting a cover over the Amiga when people are trying to do the electrics, with bits of plaster flying everywhere as I try to circum-navigate Hockenheim for the 27th time.
It creates an unusual sound to the boot-up sequence, with everything going as normal, then the hard drive spins faster and faster, making an increasingly worrying sound before you opt to turn the damn thing off.
Computer vacuum cleaners are under-rated, in my opinion. It's turned out to be a lifesaver twice now.
Of course, wiggling the Squirrel SCSI adaptor to fit the CD-ROM into the PCMIA slot so much that eventually one (ONE!) pin breaks in the PCMIA slot, rendering gigabytes stored on CD useless. Noooooooo!
Thank heavens for WinUAE. I could play Superfrog again (except then my Virtual grand Prix CD was too scratched! After 2 years of waiting to play it again! Augh!)