There is a common Western saying that "How can you be good without belief in God?" The philosophy behind that saying are two deep questions: "What is good?" "Why do good?" In places with theistic cultures, the answers can be simple: "God says what is good." "Doing good for God."
But who told us what God says? Human. So the real situation is: human religious authorities tell us what God says what is good.
Andy Thomson was right on the point, "Secular morality means doing what's right regardless of what we've been told; religious morality means doing what we've been told regardless of whether it's right." Some might criticize that "what's right" is also told by some other authorities. This "what's right," while certainly cannot totally avoid cultural influence, also invoves judgment by conscience, and, most importantly, open to questioning and revisions. The spirit is to decide by yourself what is right, not by how you are told.
The answer "Doing good for God" for the question "Why do good?" reveals another thought behind: "good doings need recognition." What's more, a commmon Western belief is that God rewards good doings in heaven. A question immediately follows: is doing good for goodness sake more noble than doing good for some other end? Is it meaningless to do good without somebody recognizing? So, the core difference between theisitc morality and secular morality can be summerized by these very short statements:
Theistic morality means doing good for recognition, if not for reward.
Secular morality means doing good for goodness sake.
Which one is more noble? You decide.
