Live wire and ground question
I have never tried it, but I am pretty sure if I put a live wire on my
  floor, nothing will happen, right ?


Electricity will flow through the floor to ground or whatever object has a different voltage potential than it. The resistance of the floor will probably be high, so not much current. The capacitance of the wire with other objects will also allow current to flow. Any two conductors make a capacitor.


  So why when touching my body the electricity find the earth


It travels through the air via capacitance, and essentially turns you into an antenna at 60Hz. It doesn't take much to get a few mA, enough for one to feel it. Your body makes an good antenna/capacitor, because of the partially conductive surface area of the skin.