of Subject-Verb Agreement

Here's the basic rule again.  What does it imply?  What grammar does a student have to be able to handle to carry out this process?

Basic SVA Rule

If the subject is a singular noun or s/he or it, a present tense verb adds -s.  The -s form of have is hasBe has present tense forms am, is, are: I am; s/he it it; you, we are. Be also has past tense forms: was and were: I, s/he, it was; we, you, they were.

1. noun types Count and noncount, plural forms, irregular plurals
2. pronoun forms I, you, me, he, she, it, we, you, they
3. forms of be the most irregular noun of all--and sva happens with past tense as well as present tense forms
4. present tense forms but not just simple present tense--also, present perfect and present progressive and present perfect progressive
5.forms of have has as well as have
6.  strange cases Collective nouns, titles, compounds of various sorts, none and other abstract pronouns
7. noun replacement units infinitives, gerunds, noun clauses
8. spelling and pronunciation adding the final -s spelling isn't nearly as difficult as getting the pronunciation right with 3 choices: smiles, buzzes, laughs

also students are not going to hear these endings easily since they are often blended right into the following word--or dropped.  And the be forms are often contracted, especially when used with the present progressive

10. recognizing the subject of a sentence  For many students, sva is difficult because they do not understand which words and phrases make up the subject of the sentence.  For example, if the sentence begins with an adverbial, these students can be confused.  Or, if the subject is a long one with a prepositional phrase or a relative clause as a post-modifier.   
what did I forget? Please email me your questions and comments.