The subject tells whom or what the sentence is about, and the predicate tells what the subject is or does.
Example: The dog ran.
Explanation: The dog is the subject of the sentence, because the sentence is telling something about that dog.
A book of maps is an Atlas.
Queen Victoria is the widow
I think that the best way is making a friend or teacher check it before you turn it in. So they can give feedback, catch errors, or anything else