to understand how things work, not to be naive about things
In the song "New York City Girl", the singer tells the New York City Girl that "you should know the score by now". Meaning she shouldn't be so naive. She shouldn't think that love is going to be like the Broadway shows, i.e fairy tale like. She's had enough bad experiences to know better, "to know the score by now"!
by L. Centeno November 13, 2006