In your case of 9L and 9R, just use your noggin. Would it make sense to have departing traffic turning head-on into each other and would it be logical to have arriving traffic flying head-on on base and dodging over and under each other to get to final? Maybe in mainland China but hardly anywhere else.
Typically, 9L would be left traffic and 9R would be right traffic. On departure, two aircraft would be turning away from each other or flying parallel. On arrival, two aircraft would be approaching head on but turning final way before they got close (hopefully) or flying parallel straight-ins. The latter case can lead to some interesting comments in the passenger cabin if, for example, the plane bound for 9L is flying a long straight-in final and the plane bound for 9R is on base leg and headed directly towards the one bound for 9L.
Runway spacing and sidestep approaches mess this up a bit, so be alert and pay attention to what the tower controller is telling you. Reading back the tower instructions is a good way to make sure that you understand what's happening. You might get something like the following if inbound straight in to, say, 9R: "Cessna 123, you're number 2 to land behind the Citation sidestepping from ILS runway niner left." Be sure to tell the controller whether or not you see the Citation; for example, "Roger, 123 has the Citation" or "123, no joy on the Citation." Remember that the Citation is probably below you and can be lost in ground clutter or haze so keep up with its position.