This is one of the most maddening things to have pop up in your mind all the time. You want to discover out, but don't know how to go about doing it. Sometimes the direct approach is best--just ask. But if that seem too bold for your liking, look for the next signs.
Pay attention to your conversation with the person in question? Does this person show a special notice in having a conversation with you and, once started, make an effort to keep that chat going?
Is this person "by chance" running into you in seats where he or she knows you will be, such as at your desk? At the Laundromat on Tuesdays? At your brother's birthday party?
Build a note if he or she mentions future plans to spend time with you: "That band is coming to town soon. We should really get tickets."
Spend time alone jointly. Canceling other tactics in order to be with you longer, or not finding excuses to leave, could be a symbol of interest.
Has he or she been calling for possibility like, "I was wondering if you knew what that pizza place down the street is called," followed by, "Are you hungry?"
Has this person taken a sudden attention in your life and hobbies? This is a sure sign that he or she is interested in something - and it's probably not your trample collection.
Watch how the person acts approximately your friends - he or she might be extra friendly to your neighboring pals for a reason.