In a sentence, when you are listing things do you use a comma before the and in the sentence. Example: I like toast, eggs, bacon and hashbrowns for breakfast.
I do.
It depends on the style manual you are following.
'I like bacon and eggs, toast and jam, and yogurt for breakfast.'
'I like yogurt, cereal, and toast for breakfast.'
'I like yogurt and bacon and eggs for breakfast.'

The comma is a clarifying tool.