Alcoa (AA) squib-kicks the earnings season into gear tonight. The aluminum kingpin is expected to report profits of 6-cents a share on about $5.6 billion in revenues. In the same period last year, Alcoa lost 3-cents a share on about $6 billion in revenue.

According to Thompson Reuters analysts are expecting member companies of the S&P 500 to report $25.55 of earnings, a 2.8% rise over the fourth quarter of last year. The same analysts expect the top-line to increase 1.9% for the quarter, a reversal of the 0.8% drop seen in Q3.

The Wall Street Journal reports that consensus EPS forecast for Q4 was 9.9% growth as of early October. The drop in optimism likely reflects the trail of tears that was the news flow into the end of 2012. This negative drumbeat included Hurricane Sandy and the harrowing fiscal cliff debate. Regarding the latter, CEO's couldn't have been more clear in voicing concerns over the degree to which dickering in DC was damaging their business results and outlooks.

Though the art of sandbagging - forecasting weak results then beating those estimates - is a time honored Wall Street tradition when seemingly every CEO in America complains about the same thing it's hard to ignore.

Spoiler Alert: Estimates are too high for Q4 and that may be okay.

The last 3 months of 2012 represented a perfect opportunity for corporate America to reset expectations and miss estimates with impunity. Any lingering fundamental problems or issues can and will be stuffed into the quarter and blamed on the laundry list of headwinds at the end of last year.

Related: Rolling into Q4 Earnings Season With Low Expectations

Investors need to watch two things as earnings season progresses. First, how the market reacts to what are most likely to be weak results. Second, and more important, is the guidance for 2013. The trillion question facing markets is whether or not weakness at the end of 2012 was fleeting. If the economy can crank back up again early this year, stocks are cheap. If instead corporate America is seeing a fiscal cliff hangover that could last through the first half of 2013, markets could get sloppy to the downside.

More than any quarter in recent memory, Q4 reports won't be about the numbers, but the guidance. Ignore the headlines and wait for the conference calls.