Hi ghnlrug,
In general, most GMAT questions ask a straight-forward question (re: What is the value of X? Is Y/Z an integer? What does the scientist assume about the study? Etc.), but as you perform at higher-and-higher levels, the Test will adapt to you - and you'll be more likely to see questions that 'test' the thoroughness of your thinking. While you won't necessarily see lots of questions in that format (even if you're doing really well overall), you might see questions that require more effort (re: What is the sum of all of the possible values of X?). Based on the wording of the question, you can infer that more work might be needed; in the prior example, note how the prompt did NOT ask for the value of X or the "sum of the two values of X" - it asked for the sum of ALL of the possible values of X).
Regardless of what specific question is asked, your focus should be on doing organized, strategic work on your pad (NEVER "in your head") because that's the most efficient way to approach just about every question on the GMAT (and that's what Business Schools will expect of you). You should also keep in mind that NOTHING about a GMAT question is ever "random" - every word in each question is carefully chosen (and even the format of the 5 answer choices is carefully chosen) so you should pay careful attention to those details. You'll find that most questions require 3-5 'steps', but the individual steps are rarely all that difficult - and if you think that a question is too hard or too weird, then you should 'dump it' and move on.
GMAT assassins aren't born, they're made,
Rich