Coordinators (and, but, so, or, nor, for*, yet*) connect elements of equal importance.

S + V , but S + V S + V and V S or S + V N and N Adj. and Adj. Phrase and Phrase Can be used in a series: A, B, C, or D

(A comma is normally used) (No comma is necessary)

Examples:

He drinks coffee, but she drinks tea.

(S + V , coordinator S +V)

Gary lives in Ohio, and Deana lives in Michigan.
She loves to dance, so she bought a studio.
You could buy a car, or you could put the money in the bank.

When there is a new subject and verb, a comma is used before (not after) the coordinator.

I hate to sing but, I love to dance. (Incorrect)
I hate to sing, but I love to dance. (Correct)

John and George both play football. Paul listens to music and reads books. John, Paul, George, and Harry are classmates.

(two subjects) (two verbs) (series)

* For is also commonly used as a preposition. Yet can sometimes be used as an adverb.