I'll forever be grateful for my AP Language Arts teacher who taught me more about English in one year than all my other teachers combined (maybe that's an exaggeration). One of the most important subjects Dr. K. touched on was personal pronouns (he, us, I, we, etc.).

Here's a chart—featuring my bad handwriting—she had my class create to sum up everything:

This is the cheat sheet for that moment when you're staring at a sentence and thinking, "Do I use 'I' or 'me'?"

Basically, you use 'I' when it's the subject or is following a linking verb. The most common linking verb is 'to be' and its various forms (is, are, was, am, been, etc).

Examples
*I underlined 'to be' forms to help

I love to procrastinate.

Miles and she lost their dog.

The evil character in the novel was he.

Sally and I promised to help her.

It must have been they in the room.

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However, object pronouns are always confused with subject pronouns. I think that they're easier to identify because the rules they follow are much simpler.

A. They follow transitive verbs (non-linking verbs)

or

B. They follow prepositional phrases

Examples
*I underlined the beginning of prepositional phrases to help

The boys cheered for us during the volleyball game.

My dog's barking startled her.

We all saw him score the winning touchdown.

Lucy will meet Mary and them at the dance.

The police officer walked over to me and Jane.

Tip: When you're really stuck on deciding if it's "X and me" or "X and I", just remove that other person (X) from the sentence and see if it makes sense.

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Some of these sentences don't sound right, but they are grammatically correct. I took all of them from the worksheets my teacher assigned.