What is importance of Mashwara,meaning in English Suunat, etiquette, Adab and Quran Ayat surah shura,Ale Imran about it, Hadith its Dictionary and literal use advice for Dawah worker

 Mashwara literary meaning is Consultation and Suggestion. 

In Islam it has a broader and special meaning. It is a Command of Allah described it as a quality of Muslims. (Surah Shua 38)
 وَالَّذِينَ اسْتَجَابُواْ لِرَبِّهِمْ وَأَقَامُواْ الصَّلوةَ وَأَمْرُهُمْ شُورَى بَيْنَهُمْ وَمِمَّا رَزَقْنَـهُمْ يُنفِقُونَ 

42:38 And those who answer the Call of their Lord, and perform the Salah, and who (conduct) their affairs by mutual consultation, and who spend of what We have bestowed on them.
Our beloved Prophet Sallallahu Alaihi Wasallam did it on the commands of Allah. (Ale Imran Ayah 159) 
وَلَوْ كُنْتَ فَظّاً غَلِيظَ الْقَلْبِ لاَنْفَضُّواْ مِنْ حَوْلِكَ فَاعْفُ عَنْهُمْ وَاسْتَغْفِرْ لَهُمْ وَشَاوِرْهُمْ فِى الاٌّمْ 

3:159 And by the mercy of Allah, you dealt with them gently.And had you been severe and harsh-hearted, they would have broken away from about you; so pardon them, and ask forgiveness for them; and consult them in the affairs.

Khulfae Rashedin constantly did it throughout their Period.of  if it is done with Proper intention it will become Important Sunnah.
It is Important to note that Maulana Ilyas drew attention on this sunnah,and he made an Integral part of effort of Dawah and Tabligh.In Tablighi Jamaat everything is done by Mashwara. May Allah give us Taufeeq