Sacre Coeur is amazing. Take the tram up! We walked all the way up (it's the highest point in Paris) and THEN saw the tram on the opposite side. Also, getting a museum pass and a metro pass is a NECESSITY. The museum pass allowed my group to bypass the lines at D'orsay. When we left, several hours later, we saw some of the same people still in line. The metro pass was very nice, as well.
