In English, a subject is the person or thing that is doing the action or being talked about in the sentence. You can’t do much wrong when you have the actual name of a person, place, or thing as the subject, but pronouns are another story.
Legal subject pronouns include I, you, he, she, it, we, they, who, and whoever. If you want to avoid a grammatical felony, stay away from me, him, her, us, them, whom, and whomever when you’re selecting a subject. Also avoid the –self pronouns (myself, himself, herself, ourselves, and so forth) when you're scouting out a subject, unless you throw one next to another subject for emphasis, as in I myself will select the proper pronoun.
Here are some examples of pronouns as the subject of a sentence:
I certainly did tell Lulu not to remove her nose ring in public! (I is the subject of the verb did tell.)
Al and she will bring their killer bees to the next meeting of the Unusual Pets Association. (She is the subject of the verb will bring.)
Whoever marries Larry next should negotiate a good prenuptial agreement. (Whoever is the subject of the verb marries.)
Most people do okay with one subject, but sentences with two subjects are a different story. Would you say something like this?
Robert and me are going to the supermarket for some chips.
Although her and I haven’t met, we plan to have dinner soon.
See the problem? In the first sample sentence, the verb are going expresses the action. To find the subject, ask who or what are going. The answer right now is Robert and me are going, but me isn’t a subject pronoun. Here’s the correct version:
Robert and I are going to the supermarket for some carrots and celery.
One good way to check your pronouns is to look at each one separately. Isolating the pronoun helps you decide whether you’ve chosen correctly. You may have to adjust the verb a bit when you’re speaking about one subject instead of two, but the principle is the same. If the pronoun doesn’t sound right as a solo subject, it isn’t right as part of a pair either. Here is an example:
Original sentence: Ella and her went to the spitball-shooting contest yesterday.
Check 1: Ella went to the spitball-shooting contest yesterday. Verdict: sounds okay.
Check 2: Her went to the spitball-shooting contest yesterday. Verdict: sounds terrible. Substitute she.
Check 3: She went to the spitball-shooting contest yesterday. Verdict: much better.
Recombined, corrected sentence: Ella and she went to the spitball-throwing contest yesterday.