MILLBURN, N.J ( TheStreet) -- The holidays have come and gone, and earnings season is once again upon us. Here are four things that The Finance Professor will be focusing on as companies report their fourth-quarter earnings over the course of the next few weeks.1. Revenue Growth 2009 was marked by net income stabilization and moderate growth, a feat achieved primarily through cost reduction. Top-line revenue growth, however, was stunted due to poor comparisons with the prior year and a strengthening U.S. dollar. If we are truly going to experience an economic rebound, earnings growth is going to have to be sourced from top-line revenue growth. Indications are that holiday season sales were better than expected. This was due to both improving consumer demand and smaller markdowns taken by retailers. The real test for revenue growth will come from the domestic retailers, especially the big box stores such as Macy's ( M) and J.C. Penney ( JCP), and from multinationals such as International Business Machines ( IBM) and Merck ( MRK). Also, look for gross credit and debit charges from the big credit card processors, such as Visa ( V) and MasterCard ( MA).