A few things my boys have learned from their friends who are girls:
Girls like to play House.
Playing House involves someone being the mom, someone the dad, and someone the baby.
The baby crawls, coos, and cries, and is to be comforted by the person playing the mom (or the dad if the mom is busy making plastic-food dinner).
When playing Castle (another girl-friend favorite), the prince is supposed to kiss the princess if a witch has poisoned her with a bad apple.
If the princess is captive in a tall tower, the knight or prince should save her (the boys knew this one already...that's where a good sword comes in handy).
A carriage is something pulled by horses that a princess rides in, preferably with a prince, on her way to a royal ball. The family minivan can be substituted in a pinch.
Many girls are afraid of *squirrels and wouldn't particularly care to chase after them.
*Substitute any rodent here.