Varun's house: When Sanjana is looking inside, he leaves behind a half-smoked cigarette that flies off when she touches it. He's also heard running off. Seen only in a hood. Tattooed arm.
Westwood College: First he sneaks into the girls' washroom when nobody is inside, and leaves behind another piece that shoots off when touched. He's also likely to have written the message and left behind that candle.
Westwood College: Then he's standing to the left side in the candle march, only to disappear, and reappear at the video player console, putting in his DVD. That DVD has got some recordings that feature him and a smiley sign that become creepy.
Outside Ela's house: He just stands and watches. More tattoos. Sanju and Vinnie are there.
Nirala Photo Studio: Located in some mall. He picks up photos of the candle march. He even crashes into Sanju briefly! We also see his eyes, and briefly his mouth- he has no facial hair, except for a light stubble. Plenty of tattoos.
From the mall, to the party site: He drives the new DZire very fast, and then leaves behind another coded message on trees, and is seen all day, but vanishes into the night. This car is eventually revealed to be bought by Sanju's dad, but stolen by the mystery man.
Pizza delivery: That creepy smiley from the freak video at the candle march reappears on his shirt. This time, Sunny gets a clear view of the man. Sunny becomres a lot more important than we thought.