I hope that you saw this year's U.S. Open. It was very exciting and informative. Here are some observations I got from watching that might be of benefit to you.
After watching matches played by Patrick Rafter, Mark Philippoussis and Lindsay Davenport, I began noticing a similar trend. This trend entailed attacking the net after the return of serve, especially the second serve. Sounds simple doesn't it? However, I cannot remember seeing it done so often and so well as displayed by these players.
Just imagine playing offensively on your serve and then playing offensively on your opponent's serve. What typically happens is that most club players tend to play aggressively on their serve, but play conservatively (defensively) on their opponent's serve. Take notice how Mark Philippoussis chipped/blocked his opponent's second serve and rushed the net. Typically, Philippoussis was always known as a tremendous server and power player, but in the big matches he always racked up more unforced errors than winners. Look how Lindsay Davenport made minced-meat out the Martina Hingis' second serve by moving in several feet inside the baseline to attack the net after the return.
Now remember how many times Patrick Rafter attacked the net after the return of the second serve on the way to his second consecutive U.S. Open Singles Title.
Get the message from these great players. Often, your opponent's second serve is one of their weakest shots. Do not reward their conservatism by just getting it back. Be aggressive, follow it to the net and become more offensive.
Good luck on the court.