When aliens spot Earth, what will they see?

Researchers have made incredible advancements in the detection and study of exoplanets in recent years, spotting literally thousands of new planets and learning tantalizing details about them. Scientists can often tell how warm a planet's surface is, what its atmosphere is made of, and whether or not it could hold liquid water on its surface. All of this information helps in the never-ending search for extraterrestrial life, but what if an intelligent race of aliens were looking at us? Would the...