"educated guessing" just means consciously identifying wrong answers (and crossing them off, of course!)

For SC, that's simply going to mean: deal with whatever grammar issues you can deal with and then guess from among the remaining answer choices.

For RC and CR, that means spending some more time paying attention to how the test-writers craft wrong answers.

Follow this link for some ideas for RC wrong answers: https://www.beatthegmat.com/verbal-strategy-t14035.html

CR wrong answer types tend to be tied to the type of question you're doing.

For example, on draw a conclusion, the most common wrong answers try to get you to go too far - to make assumptions and infer things that aren't 100% supported by the passage.

On strengthen, weaken, the most common wrong answers don't address the given conclusion (both types ask you to do the action to the conclusion - eg, strengthen the conclusion). It's not necessarily enough to strengthen or weaken a premise - you actually have to strengthen or weaken the conclusion itself.

For find an assumption, your task is to find something that MUST be true to tie one of the premises to the conclusion (there's that conclusion again). The most common wrong answers will discuss something related to premise, but they will not actually have any bearing on the argument's conclusion.

For all types, there's also the "bad logic" wrong answer type - the answer that actually does the opposite of what you'd want for the right answer. These can be tempting if you're reading too quickly and not really thinking through what's going on logically.

For both RC and CR, when studying, add this task to your list of things to study: what do I think is the most tempting wrong answer? Why is it so tempting? (this allows you to categorize the wrong answer type - to see how they might try to trick you) Why is it wrong even though it's so tempting? (this, of course, allows you to avoid the trap!)