The accuracy of the verbal expression depends on clear thinking. Find a good textbook on logic and pay attention to the sophistry - the science of logic deft fraud. Learn to distinguish between sophistry in speech, especially a lot of tricks you will find in the statements of politicians. Learn all kinds of sophistry, so you can call each of them in Latin and explain what it is. Such explanations improve logical thinking. Train at first only with close, and only then can transfer their skills in the professional field of communication. The main thing - do not criticize aloud chiefs, although for myself sophistry can celebrate and collect on each "logical compromising" - an exciting experience and useful for careerist.
Good register on the forum or blog dedicated to your hobby. There are going to witty people who can borrow wording or principles of certain phrases. Set a goal to become a popular figure in the forums and blogs. It will have to work on your style and style, but the ability to hone great idea trains during such activities. You can write to one of those who particularly like the style, in private, and establish a personal relationship that will contribute to your own verbal development. Learn better skills directly from the master.