How should one teach the Dhamma to others? Answering questions here in buddhism.stackexchange.com is often Dhamma teaching, or at least an effort of it. How can that be rightly done?
I think most of the people contributing on Buddhism.SE do not qualify to call themselves Dhamma teachers. Their answers also cannot be considered a Dhamma teaching.
The following is a better approximation, from Mahāgosiṅga Sutta (MN 32):

“Reverend Sāriputta, it’s when two mendicants engage in discussion
about the teaching. They question each other and answer each other’s
questions without faltering, and their discussion on the teaching
flows on. That’s the kind of mendicant who would beautify this park.”


As a side note - a question arose in the comments whether the MN 32 quote should be translated as &quot;about the teaching / Dhamma&quot; (Sujato translation) or &quot;on the higher Dhamma (Abhidhamma)&quot; (Bodhi translation).
The following opinion by Bhikkhu Analayo supports the Sujato translation.
From pages 70 - 71 of the book &quot;The Dawn of Abhidharma&quot; by Bhikkhu Analayo:

In the Mahāgosiṅga-sutta and its Madhyama-āgama parallel the reference to “abhidharma  talk”  or  to  discussing  the “abhidharma”
occurs alongside “Dharma talk” or “teaching the Dharma”. This gives
the impression that the two terms Dharma and abhidharma are here
interchangeable. In the Mahāgosiṅga-sutta,  the  prefix abhi- would
thus  convey the  sense  of “about”  or “concerning” the Dharma. The
passage  would then describe having a talk “about the Dharma” and
discussing “about the Dharma”, abhidharma.49
The notion that the prefix abhi- conveys a sense of superiority appears to reflect a later understanding of the implications of the
term. In line with later understanding, the commentary on the
Dhammasaṅgaṇī, the Atthasālinī, refers to the present passage in
support of the authenticity of the Abhidharma-piṭaka as the Buddha’s
word.50
A discourse in the Aṅguttara-nikāya describes a group of elder monks seated together “talking abhidharma talk”.51 In this
case the Madhyama-āgama parallel does not employ the term abhidharma
at all, but rather describes that these monks were “wanting to settle
a matter of dispute, namely  to  discuss  what  is  Dharma  and
Vinaya,  what is the  Buddha’s teaching”.52 This case would
be in line with the impression that abhidharma talk can simply stand
for talk about the Dharma.