Compounding involves having more than one of a grammatical element (subject, verb, object, etc.). If you have a compound subject, all subjects would refer to the same verb. For example (subjects are underlined):
Cool breezes, blooming flowers, and warmer temperatures mean that spring is on the way.
A compound subject almost always takes a plural verb, but sometimes, phrases become singular to our ear, or we sense that they are a unit, especially when the noun they refer to is singular:
Peanut butter and jelly is my favorite sandwich. (The subject complement, sandwich, is singular, so the compound subject peanut butter and jelly is singular.)
Some abstract subjects should be treated as singular if they are commonly considered a conceptual unit:
Peace and quiet is rare in this office.
When a compound subject is joined by “and” and is modified by “every” or “each,” the verb is singular:
Each boy and girl is to memorize a poem.
Every one of us is responsible for our choices.
When a compound subject is joined by “or,” “neither…nor,” or “either…or” the verb should agree with the subject closest to it.
Neither my friend nor I want to see the movie.
My dad or my mom drives me to school.
When you begin a sentence with a verb and the subjects follow, decide whether you have one or multiple subjects and make the verb agree:
Enclosed are a resume and letters of reference. (If you turn it around, agreement is clear: A resume and letters of reference are enclosed.)
When the verb follows a subject placeholder like “there,” and then the “real” compound subjects follow the verb, it isn’t so simple. I would use what sounds natural, and not use an awkward verb because it may follow a “correct” rule. This is considered “notional agreement” when the number of the verb is affected by the noun closest to it. I’ll discuss this in another tip.
Remember that a regular plural verb does NOT end in /s/, while a singular verb often does (just the opposite of nouns).