The adjective sycophantic is perfect for describing someone who uses flattery to get what they want. The sycophantic guy in your biology class might compliment the professor on her fabulous shoes as he hands in his lab report.
Someone who's sycophantic goes overboard with compliments, usually to gain some kind of advantage. You see sycophantic behavior in Hollywood all the time, from red carpet interviews pouring flattery on movie stars to fawning autograph seekers. Sycophantic comes from the Greek word sykophantes, "one who shows the fig," a vulgar gesture of the time. The reference is to hypocritical Greeks behind the scenes who pretended to flatter while encouraging others to "show the fig."