The eyes can reveal many things about a person, and can give emotions away. If you have met an interesting person at a function and he/she gives you long, lingering looks, perhaps in a very sensual manner, you can rest assured that the person is interested. Deep or shy gazes, and frequent, discreet glances in your direction mean that there's something brewing in his/her mind.
Make it a point to notice the person's hands when you are conversing with him/her. Running fingers through the hair, or twirling strands of hair around the fingers is often a sign the person is interested in you. He or she may even have subconsciously copied your seating stance, and may flash a brilliant smile every time you look into his/her eyes.
If the person you think is attracted to you is from your circle of friends, you are bound to experience him/her getting touchy, a little more than usual. Holding the arm gently, or touching the hand for a little longer than required are all signs you should look out for.
When a person takes an interest in your hobbies and likes and dislikes, it is a sure sign of romantic inclination. The person is bound to make more efforts to get to know you better. He/she may start to hang out at the places you frequent, or may even try to accompany you to different places. He/she may call you often, or take a genuine interest in your circle of friends and your family.
A sudden interest in your life is a clear indication that tells you if a person is attracted to you. This is simply because he/she wants to know you better. Finding excuses to spend time with you is yet another sign. If you both enjoy each other's company, then what's stopping you from returning the sweet gestures?