What is a class A player?

This is not such an easy thing to define.   For one thing, it is a moving target.   The typical A player of today is probably more knowlegable and a better player than the typical A player of 20 years ago.   The influx of large numbers of children into tournaments has actually brought down the average rating and made those points tougher to get.   A great many A players today were once Experts.   They haven't become worse players, but there has been a nation wide ratings deflation.   Fortunately, the U.S. Chess Federation is trying to reverse this downward trend of ratings.  

There are many different styles of Class A players.   Some are tactical wizards, and others are slow positional trench warriors.   Some A players know their endings, but others are absolutely terrible at them.   Some A players know their openings, and some "play by the seat of their pants."   (The "seat of the pants" opening has won many games.)            

There are certain characteristics, however, that are common to all A players.   Most can play speed chess reasonably well.     Most are pretty good at tactics (which is why they can play speed chess.)   Most see simple combinations and mates instantly.   It is rare that they fall into obvious blunders like hang a piece, even when in time pressure.    

Just being good and fast at tactics is what allowed me to cross into Class A almost 20 years ago.   I have often said that a person can become an A player by just studying tactics because it worked for me.   But modern A players need to have a better understanding of the openings and other aspects of the game.