First:
You must know every single terrain of the map where you are in. For example, in Shanghai, in the docks you can here footsteps on the wooden bridge.
Second:
People in SF make mistakes of firing against their teammate, therefore wasting bullets. So here's the second step. Know where your teammates are. Use the in-game HUD/ heads-up-display. The YELLOW names.
Third:
And if you're on your own and 2 other opponents, you'll still know where the opponent will come from. Unless he/she is crouching. Thus, depending on your place where you are waiting, let's take for example the ware ware box B, you are in defense, anticipate that all direction where your opponent will come out, the left side when he passed you, the only way he/she can come through is ware B inside.
Hope I helped.
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