Dale Carnegie, one of the most popular self development gurus of all time, knew the secret to developing real friendships and relationships was to become genuinely interested in other people. Carnegie outlined how important birthdays are to an individual's identity. That is what I love about Facebook: instant access to birthday information. If I go out with a girl, I always find out when her birthday is. It is one of the most important days in their lives. Understanding this, you are able to be there when they want to feel most appreciated. Depending on your style, I always like to add the girl on Facebook for this simple reason: to have the date of their birthday so I am there to show them love and appreciation when it matters most. It will separate you from the other guys who forgot or didn't put in the effort to find out when the girl's birthday was.