Is there any standard to identify whether your post is in quality or not?
There is no standard, post quality is subjective but if you regularly out effort into the posts you make and they are helpful and relevant, many other members are bound to find them to be quality.
I've seen some posts that in my opinion are in quality but didn't get any merit.
You can report quality posts which
[self-moderated] Report unmerited good posts to Merit Source didn't get any merits here:
Is there any other way to get merit?
Other than making quality discussions, there is no other way that is ethical and within the forums rules.