I study cr collection of gmatprep, and see that there are 3

I agree that these kinds of tricks do not appear on medium-level questions. In fact, most low- to medium-level questions can be answered with "common sense" by native English speakers with a pretty good degree of accuracy; as you point out, for non-native speakers, improving efficiency and clarity in reading is key, and being able to summarize the argument is key, too.

However, the challenge of the GMAT is that, as you get better, so do the questions, SO even those who are not shooting for 700+ will see trickier questions on test day, questions which belie the common-sense approach and lead us into traps such as the above you mentioned. Here's the overall idea I'd keep in mind, that works on easier AND harder questions alike:

The GMAT is always asking about the Argument in A/S/W/F questions, NOT about the Conclusion. On easier questions, the right answer in, say, a Weakener question will simply be something that means "The conclusion is wrong" or "The prediction will not come true" or something. However, as questions get harder, this approach doesn't work, because just to argue that the Conclusion or Evidence is false doesn't really Weaken the Argument. To Weaken the Argument, pretend that the conclusion is always actually this sentence:

"The evidence I've given here is sufficient, all on its own, to prove my point."

Every author is really saying this, and it's THIS sentence that we have to weaken/strengthen on the GMAT. If we're always focused on this idea instead of on arguing for/against the Conclusion, we can develop a consistent approach that works on all difficulty levels.

Furthermore, I'm personally less about identifying trap answers and more about learning how to prephrase right answers. Yes, common traps are nice to know, but the best test-takers aren't tempted by them because they predict and find the Right Answer quickly through a solid understanding of what the GMAT is looking for in CR, as well as in RC (and, of course, in all Quant questions).