According to Harris: "The rhetorical devices presented here generally fall into three categories: those involving emphasis, association, clarification, and focus; those involving physical organization, transition, and disposition or arrangement; and those involving decoration and variety. Sometimes a given device or trope will fall mainly into a single category, as for example an expletive is used mostly for emphasis; but more often the effects of a particular device are multiple, and a single one may operate in all three categories. Parallelism, for instance, helps to order, clarify, emphasize, and beautify a thought. Occasionally a device has certain effects not readily identifiable or explainable, so I have not always been able to say why or when certain ones are good or should be used. My recommendation is to practice them all and develop that sense in yourself which will tell you when and how to use them. Rhetorical devices are aids to writing and not ends of writing; you have no obligation to toss one into every paragraph. Further, if used carelessly or excessively or too frequently, almost any one of these devices will probably seem affected, dull, awkward, or mechanical. But with a little care and skill, developed by practice, anyone can master them, and their use will add not just beauty and emphasis and effectiveness to your writing, but a kind of freedom of thought and expression you never imagined possible."
Harris cautions even as he invites us to proceed. In the table below, you'll find an organizational scheme that fixes the figures into eight categories: Tropes, Metaplasmic Figures, Figures of Omission, Figures of [word] Repetition, Figures of [clause or idea] Repetition, Figures of Unusual Word Order, Figures of Thought, and Figures of Sound. However, even in this structure (adapted from the University of Victoria's online taxonomy) confusion is bound to arise. Take the first classification: Tropes. If you were to look up the word "trope" in a standard dictionary, you would find not only its "etymology" (or origin) from the Greek tropos and Latin tropus meaning "a turn, way, manner, style," you might also discover that it is defined as a "figure of speech." Sometimes, the word "trope" is used to signify all figurative language, as in "the use of a word or expression in a figurative sense." On the same vein, it is possible to locate classifications that identify certain types of metaphor as "figures of speech" and other types of metaphor as "figures of thought." Alas, let us move on before we become mired in the classification scheme and distracted from the fun of rhetorical devices all together. But, be prepared. These ancient Greek and Latin terms can be an intimidating bowl of alphabet soup. You may find that working backwards, from the examples to the definitions, makes more sense to you.
NOTE: Robert Harris has assembled a site on rhetorical devices which can be accessed by clicking on the above link. Below you will find a table that fixes 8 rhetorical figures into a useful classification scheme.