Is it me? Or is it I?

You should know this one, it’s simple.

We know viscerally to use I in the subject of a sentence and me as the direct object:

I thanked her.

I’m the subject. I’m the doer. I thanked.

She ignored me.

She’s the subject, she’s the doer. She ignored. Whom?

Me. I’m the object of her ignoring, the direct object of the verb.

Now consider additional subjects. This is where we get screwed up:

Dennis wants to see Tracy and I in the conference room.

Dennis wants to see Tracy and me in the conference room.

The second sentence is correct. “Dennis” is the subject and “Tracy and me” is the direct object of the verb wants to see. Technically, “wants” is a transitive verb and “to see” is the infinitive, but you don’t need to know that. Just get rid of the extra person:

Dennis wants to see Tracy and I in the conference room.

Dennis wants to see Tracy and me in the conference room.

You’re still the direct object with or without Tracy. Likewise with the inverse:

Dennis and I want to see Tracy in the conference room.

Dennis and me want to see Tracy in the conference room.

Easy peasy. And it becomes second nature right away.