As a general rule, you don't tend to get more than one Emblem in any one area within a chapter, although there is an exception to this late in the game and there may well be excetions to this in the two chapters where I am missing Emblems.
You need to constantly look around your surrounds to find them as some are very distant and therefore small and you should use a sniper rifle for shooting them as lining up the laser sight on a different weapon is tedious in the extreme.
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