John H, there are several types of St Augustine. In general right now there is nothing to do. When it gets warmer the watering, bugs and diseases increase.
I have had my St Augustine for over 20 years. Every other st augustine grass in my subdivision has been replaced at least once. Why? because I found I could not maintain it properly so I have a company that takes care of it. Yes, they cost money but not as much as replacement. It was a requirement of the homeowners assn when I moved here. Today I would install Bahia or some other grass.
I think the biggest thing to watch out for is chinch bugs. Might be good to apply a preventative insecticide now if you don't know if the lawn has had them before.
Walter is very correct about chinch bugs but I thought they were treated later in the year. Brownpatch, gray leaf spot, rust, downy mildew and other diseases are all caused by fungi. Brownpatch and gray leaf spot are the most serious of these, though they don't kill it.
The problem is you must apply the correct preventative at the right time.
John, this is the time of year to apply a pre-emergent herbicide to help prevent weeds. St. Augustine should not be fertilized until the beginning of April. For a thorough guide, check out this article from the University of Florida's Extension Service: