Accurate preaching will make their preaching more convincing, and powerful. There are plenty of aids to help the preacher master the technical skills of sermon writing. The following books should be in every preacher's library. These are read, not to impress people by quoting Greek, but to understand fully the meaning of biblical words. Some doctrinal words are hard to pronounce, and even harder to comprehend, but it is your duty to study them.
Preachers make their living by speaking.
It is of utmost importance that he learns correct pronunciation, and master the basic elements of public speaking. Learn the correct usage of the language. Learn about verbs, adjectives, and all the elements of good writing. Whenever in doubt about a word, check the meaning. You must know precisely what it means, and how it is spelled.