The firing order is usually important for identifying which is which, but the numbering itself is consistent:
* Passenger Side (Right): 1, 3, 5, 7
* Driver's Side (Left): 2, 4, 6, 8
Therefore, cylinder 1 is the front-most cylinder on the passenger side, and cylinder 2 is the front-most cylinder on the driver's side. Numbering then continues consecutively from front to back on each side.