How can watching be non-doing? In  Vipassana meditation ,it is emphasized that one should not force the mind to concentrate on certain object or force anything to happen in particular.Its kind of letting things unfold and just watching them as they unfold .But for an untrained mind isn't watching by itself a kind of doing and if it shouldn't be a doing and is the natural state of restful alertness ,how can it be initiated without the mind feeling forced to do it.If one is driven by conditioning in a non doing state. 

Ardency as I understand is an important aspect of the practice ,but doing it on the razor's edge of not falling into forcing the mind,is tricky.What is the best way to initiate it so it becomes right mindfulness?.
MN1 The Root of All Things addresses watching for the untrained ordinary person as:


  They perceive the seen as the seen. But then they identify with the seen … Why is that? Because they haven’t completely understood it, I say.


In contrast, for the trained mind SN35.96 we have:


  ...in the seen will be merely the seen;...


The simplicity of "merely the seen" is itself non-doing. Ordinarily we identify with thoughts, latch onto them with greed, aversion or delusion. That latching onto thoughts is the doing to be relinquished. Yet we perceive the latching onto thoughts as "not-doing", hence the seeming paradox. 

As we practice, we start noticing the doing, the grasping. And with a measure of watchful restraint we counteract the tendency towards "doing". From AN3.60:


  When there is sense restraint, one who has sense restraint has fulfilled a vital condition for ethical conduct.
  When there is ethical conduct, one who has fulfilled ethical conduct has fulfilled a vital condition for right immersion.


Find the razor's edge between doing and not-doing. Explore that.