An old New Yorker cartoon had two men at a bar with one lamenting that “It’s hard to be a ‘between you and me’ person in a ‘between you and I’ world.”  Here are the simple guidelines that will keep people from drinking in midafternoon in mid-Manhattan and keep you putting your best grammatical foot forward.  This post will deal with just the I/me issue although the same rules apply to he/him,
she/her, and they/them.

Pronouns that refer to persons change spelling according to their use in the sentence.  That means that “I” becomes “me” in certain situations.  You have the most often used and abused situations below although there are others uses of these pronouns.  Let’s deal just with the situations that give the most difficulty.

I is used

• as the subject of a sentence, the subject of a verb.  “Tom and I are going to the Cape.”  The problem seems to arise when the pronoun is linked with another word.  An easy way to check is to take out the other word.  Most people would not say “Me is going to the Cape,” but I do hear the incorrect “Tom and me are going to the Cape.”
• after some form of the verb to be.  “It is I” is correct. 

Me is used

• after a verb as its object.  “He likes Kim and me” is correct.  “He likes Kim and I” is incorrect.  Take out the first word to check.  “He likes I” sounds as incorrect as it is.
• after prepositions.  A preposition is simply a word that links a noun or pronoun to a sentence.  The preposition “between” is a perfect example. 
  Between you and me is correct.  Between you and I is incorrect. 

Up next, thanks to a reader’s request, is who/whom.  Send along your suggestions.

Below is technical stuff.  Case indicates how the pronoun is used in a
sentence.  Nominative is the subject of a sentence or follows the verb “to be.” 
Objective case follows verbs and prepositions.

Nominative                  Objective
case                            case  

I                                 me

he, she                        him, her

we                              us 

they                            them