Reviewing the advice of al-ʿAllāmah ʿAbd al-ʿAzīz ibn Bāz (raḥimullāh), the person who wishes to engage in daʿwah must have knowledge of what he calls the people to and what he forbids them from. He does it with sincerity, not for fame seeking, only for Allāh's sake, no partisanship or blindly following one or the others opinion.
Strive in sincerity (when giving daʿwah), strive in the paths given by Allāh; kitāb, sunnah, salaf, ḥadith, athar. Leave the philosiphers to the innovators. If your are not able to do that then aid those who can, as dawah is not for everyone.
Say (O Muhammad: "This is my way; I invite unto Allāh (i.e. to the Oneness of Allāh - Islamic Monotheism) with sure knowledge, I and whosoever follows me (also must invite others to Allāh i.e. to the Oneness of Allāh - Islamic Monotheism) with sure knowledge. And Glorified and Exalted be Allāh (above all that they associate as partners with Him). And I am not of the Mushrikūn (polytheists, pagans, idolaters and disbelievers in the Oneness of Allāh; those who worship others along with Allah or set up rivals or partners to Allāh)." [Yūsuf, 12:108]
Key points include:
Daʿwah requires both sincerity and knowledge, many lack one or the other
Giving daʿwah is not about seeking the pleasure of the people nor gaining followers
We do not get bothered when the people boycott, turn on you, abandon you, warn against you, speak ill or lie upon
What is important to the sincere believer is the pleasure of Allah and fleeing from his anger
One does not belittle or humiliate someone when giving them dawah
Allah has raised generations before you so benefit from their experiences
Sincerity is easy to lose, due to self amazement, how many have had prestigous achievements only to go astray
The caller is ardent upon the truth and he is gentle towards the one he calls to it