You probably won't have too much trouble if you approach them the same way, but there is a slight difference. Generally, in weaken/strengthen the conclusion questions, you're more likely to see a correct answer choice that brings in outside information (i.e. an entirely new premise) in order to weaken or strengthen. In weaken/strengthen the argument questions, it's unlikely that you'll see new information. Instead, the correct answer will either undermine or reinforce a premise that has already been given.
It's worth keeping these details in mind, but the same general approach should work whichever question type you see.
Hope that helps!
Tommy Wallach | Manhattan GMAT Instructor | San Francisco
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