Start with basic characteristics of the scent. Sweet, Clean, Spicy, Dry, Woody. Those are very easy to disiguish and will cancel out a lot of possibilities.
You can go even further to name some of the notes in the scent but that is sometimes hard to learn when you don't eve know the name of the fragrance.
Try to come up with a designers name or a house that it came from. This will narrow it down to just a group. With a quality like fresh and the designers name you can come up with the fragrance quite easily.