A common joke in the foreign community in Japan is that you know that you have achieved the jump from beginner to beginner-intermediate Japanese when 私 changes to 僕. Even though 私 and 僕 have the same meaning, for Japanese people in most casual occasions 私 is too formal and 僕 (or better yet, not using either) is more commonly used.
Perhaps the jump from beginner-intermediate to intermediate reading happens when learners get used to the ～ず endings. For people studying for the JLPT 2 or JLPT 3, it’s worth learning ～ず so that you can tackle the tricky reading of opinion pieces using this grammar form that crop up in exams. For the op-ed, the examiners search the web looking for the most bizarre or terrible opinions they can find to turn into questions for the exam.
As a general rule ～ず is equivalent to the ～ない ending. Therefore 行かない (will not go) would become 行かず and 食べない (do not eat) becomes 食べず. Be careful, as する changes to せず (or occasionally さず) instead of しず and 来る (to come) changes to 来ず instead of きず, so don’t get confused.
Once you have gotten used to the basic form, the first grammar form that is useful to learn is ~ずに which links two concepts to mean that you don’t do A, but do B instead. So if A is, for example, テレビを見ず (to not watch TV) and B is 勉強する (I study), the sentence becomes: テレビを見ずに勉強した (without watching any television, I studied).
Perhaps the jump from beginner-intermediate to intermediate reading happens when learners get used to the ～ず endings.
Other examples include: 彼は言わずに帰った (without saying anything, he went home), 信号を見ずに道を渡ると危ない (crossing the road without looking at the signal is dangerous) and 連絡せずに会社を休む (absent from work without contacting the company).
Another common point is ~ず plus にいる which means to continue to not do something. Some very common uses of this grammar point are お酒を飲まずにいる (I am drinking no alcohol) and 肉を食べずにいる (I am not eating meat).
A more complicated form for the more advanced students is: ~ずにいられない (I can’t help but do), which you will sometimes also see as ~ずにはいられない. A good example of this is 愛さずにはいられない (I can’t stop loving) something considered so romantic that the song Elvis Presley made famous (“Can’t Help Falling in Love”) was re-titled “I Can’t Help Falling in Love with You” in Japan. The reverse of this can be heard after someone has suffered a tragedy: 悲しまずにいられない (I can’t help but feel sorrow).
A similar form is ~ずにすむ, which means that without doing something everything will turn out fine anyway. Maybe someone sees your socks with all the incredible holes and decides to buy you a new pair out of the goodness of their heart (ahem, totally speaking from experience), you might say よかった、新しい靴下をかわずにすむ (thank goodness, now I don’t need to buy new socks) or if you found a cheap apartment that was similar to the expensive one that you were about to rent you might say 高いアパートをレンタルせずにすむ (I don’t have to rent that expensive apartment).
A popular one for exams is ~ずにおく which means that you don’t do something any more. Splitting up with your partner might make you write 彼女のメールを読まずにおく (I don’t read her emails anymore). Want to keep a secret? You might consider the similar 何も言わずにおく (I won’t say anything any more).
One if the reasons why people may not have come across this form is that it is most commonly found in written material. However, you will occasionally hear it said as a way to make a sentence easier to say. Now that you know this little tip, listen out for it in exams as it often comes up as a way to test learners.