To know if you are falling in love, observe how often you think about a person. If it is frequently and that you often find yourself smiling when you do it, then it is likely that you are falling in love. Again, you will be interested in knowing more about the person you are in to and therefore make yourself available. You will also find yourself talking about this person frequently to your friends. Check out http://www.ehow.com/how_4803883_tell-falling-love.html for details.