^^^What haggard said, also, there is no "best" way. If you wanna do a SoG or Scrog then run the lights horizontal and air cool them. If you wanna grow big ass trees in a UC system then I would run the lights vertical. There are so many techniques of growing with different mediums and different styles. Do you wanna use soil or hydro?? How many plants per light?? Give us more details of your goal and what your trying to accomplish so we can help you out.