When he was installed on the federal trial bench in 2000, John W. Darrah promised spectators he would follow his mother’s advice.That advice, Darrah said at the time, was: “Do your best, be fair and don’t think you’re a big shot.”Friends and colleagues say Darrah kept his word.Chief U.S. District Judge Ruben Castillo on Thursday described Darrah as “an accomplished jurist and dedicated public servant.”“Throughout his time on the bench, Judge Darrah demonstrated an incredible …