There are no real "traps" on the GMAT.
The key are:
Make sure you're answering the question asked.
Make sure the answer makes sense/is the best answer
Make sure you simplify the question as much as possible.
Questions on standardized tests can appear long and convoluted. Your goal is to simplify as much as possible to know "what are the test takers really asking me."
crejoc mentioned some of the traps on RC/CR questions (answers that use extreme words). Again, that simply goes hand in hand with making sure you're answering the question asked.
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