In writing poems, you are involved with different types of diction, whether you know it or not. Why become aware of the different types and use them knowingly. In one poem try to stay fairly consistent in the type you employ. In another poem, mix them all up. I took the following list from Classical Rhetoric for the Modern Student, 2nd Diction, Edward J. Corbett. Oxford: Oxford University Press. 1971.
General and Specific
Abstract and Concrete
Formal and Informal
Latinate and Anglo-Saxon
Common Words or Jargon
Referential (denotative) or Emotive (connotative)
See a related post: Word Values