I know with my son the ODD behaviors are brought on by all sorts of things, so it's hard to anticipate what will cause the next meltdown. I have learned to pick my battles with him. Some things, as annoying as they are, are just not worth the argument. It's tough, though. There are days where I truly feel like I have no control over anything here at all!
Has your son been diagnosed with aything other than ODD? Could there be another underlying cause for his behavior?