1. In a simple list:
* No comma needed: If "and" is connecting two simple items in a list, you usually don't need a comma.
* Example: I like apples and oranges.
* Comma needed: If the list is longer than two items, use a comma before the "and".
* Example: I like apples, oranges, and bananas.
2. In a compound sentence:
* Comma needed: If "and" is connecting two independent clauses (clauses that could stand alone as sentences), you need a comma before "and".
* Example: I went to the store, and I bought some milk.
3. In a series of adjectives:
* Comma needed: If "and" is connecting two or more adjectives that modify the same noun, use a comma before "and".
* Example: The house was large, comfortable, and inviting.
4. For clarity:
* Comma optional: Sometimes, you may use a comma before "and" even if it's not strictly necessary, to enhance clarity or avoid confusion.
* Example: I went to the beach, and I swam in the ocean. (The comma helps separate the two actions).
Important Note: These are general guidelines. There are exceptions and stylistic choices that can affect comma usage. If you're unsure, it's always best to consult a style guide or a grammar expert.