In the following video, Motley Fool financial analyst Matt Koppenheffer tells investors what they need to be watching when BB&T (TFC 2.83%) reports earnings this Thursday. Like we saw when Wells Fargo reported last week, a number of banks are going to be experiencing compressing net interest margins, the amount the bank keeps as profit between the rate at which they borrow and the rate at which they lend. We will want to see if these margins are also compressing at BB&T, by how much, and what the bank is doing to combat that in its other sectors where it charges banking fees.