I suck at weaken questions too, but I suck even more at strengthen questions.
One of the problems is, I tend to try to focus on the error in the passage, so sometimes I fall for the weakening answers which addresses the error(this is especially true for strengthen EXCEPT questions)...
Another problem is, strengthening is so hard to do! Sometimes I think an answer choice blocks a potential assumption and thereby strengthens, but later I learn that apparently the answer was entirely irrelevant. And sometimes I pick an answer choice which I really think strengthens the argument but apparently it's irrelevant too.
Comments
(1) Add more strength/support to believe one/or more stated premise in the passage
(2) Exclude a possible gap (assumption) in a stated premise in the passage, so that the premise is now stronger by knowing the gap is closed.
Thank you guys!