Rule 1.

SUBJECT PRONOUNS are used when the pronoun is the subject of the sentence.

Example:

______ did the job.
I, you, he, she, it, we, and they all fit into the blank .  These are subject pronouns.

Rule 2.

OBJECT PRONOUNS are used everywhere else (direct object, indirect object, object of the preposition). Object pronouns are me, you, him, her, it, us, and them.

Examples:

Jean talked to him.

Are you talking to me?

Rule 3.

HOW TO DECIDE ON USING SUBJECT OR OBJECT PRONOUNS after the words than or as, mentally complete the sentence.

Examples:

Sally is as smart as (she/her).

If we mentally complete the sentence, we can say, "Sally is as smart as she IS." Therefore, she is the correct answer.

Zoe is taller than (I/me).
Mentally completing the sentence, we have, "Zoe is taller than I am."  So I is correct here.

Daniel would rather talk to her than (I/me).
We can mentally complete this sentence: "Daniel would rather talk to her than TO me.” Me is correct.

Rule 4.

POSSESSIVE PRONOUNS show ownership and NEVER need apostrophes.
Possessive pronouns: mine, yours, his, hers, its, ours, theirs

NOTE

The only time it's has an apostrophe is when it is a contraction for it is or it has.

Examples:

It's a cold morning.

The thermometer reached its highest reading.

His coffee is cold. 

The jacket is hers.

Rule 5.

REFLEXIVE PRONOUNS - myself, himself, herself, itself, themselves, ourselves, yourself, yourselves- should be used only when they refer back to another word in the sentence.

Correct:

I worked myself to the bone.

Incorrect:

My brother and myself did it.
The word myself does not refer back to another word in the sentence.

Correct:

My brother and I did it.

Incorrect:

Please give it to John or myself.

Correct:

Please give it to John or (TO) me.