Love runs deeper than physicalities and emotions. Objectivity in those two areas will most likely result in you being able to truly evaluate whether you're experiencing love or a fling. Not to discount physicality or emotion, of course both are important, but they should not be the sole basis for pursuing another. Generally, when you meet someone, you can tell from the start whether it's going to lead to a long-term relationship where love blossoms, or whether it's just a fling and you're trying to convince yourself otherwise.
Questions to ask yourself: "Am I hoping this person will change?, Do we mutually respect each other? Am I embarrassed for my parents/family/friends to meet him/her? What is it that attracts me to this person? What do we share in common? Am I able to live in harmony with this person? Do our differences separate us or bring us together?"
Spend time with each other in a variety of settings; and as dashingscorpio said - time will reveal if you have chosen love or a fling.