1. Subject: The person, place, thing, or idea that the sentence is about.
2. Verb: The action or state of being of the subject.
3. Complete Thought: The sentence must express a full idea that makes sense on its own.
4. Correct Punctuation: Usually, this means ending with a period (.).
Let's look at an example:
The cat sat on the mat.
* Subject: Cat
* Verb: Sat
* Complete Thought: The sentence tells us what the cat did.
* Punctuation: The sentence ends with a period.