What single piece of counsel (or constructive criticism) has most improved your preaching?
Years ago I took the Dale Carnegie public speaking course. In it I learned three things that I try to practice: 1) Know your subject thoroughly. 2) Be convinced your audience needs to hear your message. 3) Have a strong passion to deliver the message. Though these principles were applied in the context of secular speeches, I found them very helpful for my message preparation and delivery.