You need to see what works best for you. Keep playing it, then play some more than play even more. It is the only way. Advice on tactics etc is all very well, you need to learn the maps and put the hours in. As that does help, no point in rushing out into bottle necks on maps or killing zones. Time my friend. You mentioned red orchestra. I have heard this is a more strategic approach to FPS. Most of the other games you mention are extremely fast paced games. Your reaction times are essential. If you are used to slower paced games you will find itt tough. Again keep plugging away mate you will get used to it.
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