Seeing how much quality stuff Don Carson produces means any tips he offers are like solid gold, he says:
Three secrets of productivity are worth mentioning:
(1) Learn to fill in the little empty periods that clutter each day.
(2) Don’t fritter. When you work, work hard; when you are not working, quit entirely.
(3) Discover how different aspects of your work can leverage other aspects of your work. For example, choosing your reading to feed into things that you’ll be preparing over the next six or nine months adds to godly efficiency.