The diagramming of sentences disrupts a fluent understanding of how language works. Worrying about how to sketch different parts of speech with a skeletal representation of words has nothing to do with exercising proper grammar. Instead, see language as a pattern that operates at three distinct but related levels: diction, or word choice; syntax, or the construction of varying sentence styles; and punctuation, the characteristic that holds these elements together logically. By defining grammar by how it works, rather than by what it is called, you remove a layer between jargon and understanding. Grammar loses its mythical power to intimidate and simply becomes a tool to use.
A complete sentence depends on a relationship between a thing and some kind of happening with that thing. A thought is not complete unless a thing (or noun) does something. That "doing" (or verb), whether it is a physical action or result of being, is also not a complete thought unless it is attached to the very thing that makes that "doing" possible. This is at the heart of a grammatically correct sentence, and it is also inherently logical. A bounce can't happen without a ball to perform it. Subjects are the people, places or things that are merely still objects until they are made mobile or existent by predicates.
Punctuation can sometimes cause great confusion because these tiny marks that look so similar can mean such different things. The comma is used to break up groups of words that are not complete sentences by themselves, unless followed by "and," "but" and "or." In these cases, a comma must be used to separate two complete sentences. A semicolon is used to join two complete sentences into a single sentence in order to emphasize their interrelatedness. It can also be used to separate items in a list that have comma-divided phrases of each item listed. A period, on the other hand, simply conveys the completion of a thought.