IF YOUR TILES ARE INTERLOCKING ALL YOU DO IS LIFT THE TILE USUALLY THE RIGHT ONE ABOVE THE ONE YOU WANT OUT AND PLACE A PEICE OF WOOD OR BROKEN TILE UNDER IT TO KEEP TILES OFF THE ONE YOU WANT TO REMOVE YOU THEN HOLD THE TILE AT BOTTOM WITH BOTH HANDS AND TWIST IT OUT THIS USUALLY POPS THE NAIL OUT,YOU THEN DRAG IT OUT THEN SLIP THE NEW ONE IN.
HOPE THIS HELPS. ONLY WORKS WITH INTERLOCKING TILES.
David Cummings., February 2010