Collected here are some of the teachings of the Buddha on sharing and teaching Dharma/Dhamma with others.
“It’s not easy to teach the Dhamma to others, Ananda. The Dhamma should be taught to others only when five qualities are established within the person teaching. Which five?
“The Dhamma should be taught with the thought, ‘I will speak step-by-step.’
“The Dhamma should be taught with the thought, ‘I will speak explaining the sequence [of cause & effect].’
“The Dhamma should be taught with the thought, ‘I will speak out of compassion.’
“The Dhamma should be taught with the thought, ‘I will speak not for the purpose of material reward.’
“The Dhamma should be taught with the thought, ‘I will speak without hurting myself or others.’
AN 5.159
Here we find some guidance on teaching with pure intentions.
“A bhikkhu teaches the Dhamma to others with the thought: ‘Oh, may they listen to the Dhamma from me! Having listened, may they gain confidence in the Dhamma! Being confident, may they show their confidence to me!’ Such a bhikkhu’s teaching of the Dhamma is impure.
“But a bhikkhu teaches the Dhamma to others with the thought: ‘The Dhamma is well expounded by the Blessed One, directly visible, immediate, inviting one to come and see, applicable, to be personally experienced by the wise. Oh, may they listen to the Dhamma from me! Having listened, may they understand the Dhamma! Having understood, may they practice accordingly!’ Thus he teaches the Dhamma to others because of the intrinsic excellence of the Dhamma; he teaches the Dhamma to others from compassion and sympathy, out of tender concern. Such a bhikkhu’s teaching of the Dhamma is pure.
SN 16.3
Here we find the Buddha speaking about teaching in different ways for different beings, as well as a description of when a person may not be a good candidate for teaching.
But the Blessed One, lord, is the unexcelled trainer of tamable people. How do you train a tamable person?”
“Kesi, I train a tamable person [sometimes] with gentleness, [sometimes] with harshness, [sometimes] with both gentleness & harshness…
…”And if a tamable person doesn’t submit either to a mild training or to a harsh training or to a mild & harsh training, what do you do?”…
…”It is true Kesi, that it’s not proper for a Tathagata to take life. But if a tamable person doesn’t submit either to a mild training or to a harsh training or to a mild & harsh training, then the Tathagata doesn’t regard him as being worth speaking to or admonishing. His knowledgeable fellows in the holy life don’t regard him as being worth speaking to or admonishing. This is what it means to be totally destroyed in the Doctrine & Discipline, when the Tathagata doesn’t regard one as being worth speaking to or admonishing, and one’s knowledgeable fellows in the holy life don’t regard one as being worth speaking to or admonishing.”
AN 4.111
For a few more resources on teaching and sharing Dharma, please see the texts referenced below.