Speak short. Your discourses are generally double the length they should be. It is possible to handle a good thing in such a manner that it loses its flavor. When a discourse is too long, the last part of the preaching detracts from the force and interest of that which has preceded it. Do not wander, but come right to the point. Give the people the very manna from heaven, and the Spirit will bear witness with your spirit that it is not you that speaks, but the Holy Spirit speaking through you. The teacher of the word of God must first talk with God, and then he can stand before the people with the Holy Spirit working upon his mind. If he faithfully cooperates with Christ, the promise will be fulfilled, “Lo, I am with you alway.” TM 311.1
Be careful never to lose a sense of the presence of the divine Watcher. Remember that you are speaking not only to an unenlightened assembly, but to One whom you should ever recognize. Speak as though the whole universe of heaven were before you, as well as the hungry, starving company of God's sheep and lambs, which must be fed. TM 311.2