BB&T (NYSE:BBT) is on deck to announce earnings for its fourth quarter and fiscal year 2012 on Thursday, and investors need to pay special attention to the following areas of that release.

Net interest margin
If other bank earnings have been any indication, investors should be paying attention to net interest margin as banks continue to release earnings. With interest rates so low, banks are finding it difficult to loan money out at pre-crisis rates, which in turn puts a squeeze on the revenue generated via interest.

Last quarter, BB&T saw an increase in total loans, which is one way to combat low net interest margin. Banking is one of the businesses in which you can make up for low margins by moving "product," and BB&T has been among regional banks increasing mortgage lending recently. If it sees another increase in total loans, a decline in net interest margin shouldn't be that big of a story.

Expansion into other markets
With acquisitions fueling expansion among banks for most of the last year, BB&T has been among the banks rumored looking to build its Florida base. One way for it to do so would be to acquire BankUnited (NYSE:BKU) and its $4 billion in assets and Miami base. If it fails in its attempts in Florida, it is already on the record with plans to open up to 30 branches in Texas, which would help supplement its acquisition of Colonial Bank in 2009.

Earnings expectations
The consensus expectation from analysts is for Comerica to report $0.70 per share in net income, which would be in line with what was expected from the bank during the third quarter. Analysts expect $2.71 in earnings from the bank, which would be an increase of 48% from 2011. It will be very interesting to see if the bank can meet these expectations, so check back on Thursday to see how they did.

Robert Eberhard has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.