This one is personal preference, but I find it annoying when emacs beeps on errors. I like knowing when something bad/unexpected happened, but the beep is too much when the sound is on and useless when muted. Add this to your
.emacs to enable a visual alert cue that flashes the frame instead:
(setq visible-bell t)
Note: From what I can tell, this only works under a windowing system, so it won’t do much good if you run emacs in terminal mode.