Best way to track down a buzzing problem?

[LordOVchaoS]

I just got don modding an SD-1 and while it sounds VERY good it has an annoying buzz when the pedal is on and I'm not playing.  Is there a way to track it down other than trial and error?

[petemoore]

  Mostly I look for a ground that isn't made or..
  Then try an audio probe to try to narrow down the suspect area'
  But yes, trial and error...
  what changed with the mods..how would that influence noise generation or pickup?
  Did you run any new or longer signal lines, or re-route wires?
  Increase gain ?