How to find out if a guy has a girlfriend?

GOT A GOOD IDEA- MEN HAVE HUGE EGOS- COMPLIMENT HIM AFTER CLASS ABOUT HOW GREAT THE WORKOUT IS...ASK FOR A COFFEE "GE TOGETHER"....THEN SOMEHOW (W/O BEING RUDE) ABRUPTLY SAY YOU GOTTA GO.......PEOPLE ALWAYS WANT WHAT THEY CANT HAVE.....ALSOREMEMBER " HE WHO CARES LESS CONTROLS THE RELATIONSHIP">>>>>>>>>>>