Music
play by ear
to play a piece of music without looking at the notes
keep your eye on the ball
to remain alert to the events occurring around one
you can't tell a book by its cover
you can't tell what a person is like from its outward appearance
spill the beans
to reveal a secret or a surprise by accident
out of the blue
suddenly and unexpectedly
jazz something up
to make something more interesting or lively
the ball's in your court
it's your turn to take action
by the book
according to the rules
simmer down
to become quieter and calmer
green with envy
very jealous
all that jazz
et cetera and so forth
hit someone below the belt
to do something unfair to someone
hit the books
begin to study, to study
bring home the bacon
to earn a salary
tickled pink
greatly pleased
tune out
ignore someone or something
make a splash
crack a book
to open a book to study
chew the fat
to chat informally with close friends
rose-colored glasses
a cheerful or optimistic view of things usually without valid basis