Greet people with salam first

أَنَّ رَجُلاً، سَأَلَ النَّبِيَّ صلى الله عليه وسلم أَىُّ الإِسْلاَمِ خَيْرٌ قَالَ ‏ "‏ تُطْعِمُ الطَّعَامَ، وَتَقْرَأُ السَّلاَمَ عَلَى مَنْ عَرَفْتَ، وَعَلَى مَنْ لَمْ تَعْرِفْ ‏"‏‏.

“A man asked the Prophet, "What Islamic traits are the best?" The Prophet said, "Feed the people, and greet those whom you know and those whom you do not know”

النَّبِيِّ صلى الله عليه وسلم قَالَ ‏ "‏ خَلَقَ اللَّهُ آدَمَ عَلَى صُورَتِهِ، طُولُهُ سِتُّونَ ذِرَاعًا، فَلَمَّا خَلَقَهُ قَالَ اذْهَبْ فَسَلِّمْ عَلَى أُولَئِكَ النَّفَرِ مِنَ الْمَلاَئِكَةِ جُلُوسٌ، فَاسْتَمِعْ مَا يُحَيُّونَكَ، فَإِنَّهَا تَحِيَّتُكَ وَتَحِيَّةُ ذُرِّيَّتِكَ‏.‏ فَقَالَ السَّلاَمُ عَلَيْكُمْ‏.‏ فَقَالُوا السَّلاَمُ عَلَيْكَ وَرَحْمَةُ اللَّهِ‏.‏ فَزَادُوهُ وَرَحْمَةُ اللَّهِ، فَكُلُّ مَنْ يَدْخُلُ الْجَنَّةَ عَلَى صُورَةِ آدَمَ، فَلَمْ يَزَلِ الْخَلْقُ يَنْقُصُ بَعْدُ حَتَّى الآنَ ‏"‏‏.

“The Prophet ﷺ said, "Allah created Adam in His picture, sixty cubits (about 30 meters) in height. When He created him, He said (to him), "Go and greet that group of angels sitting there, and listen what they will say in reply to you, for that will be your greeting and the greeting of your offspring." Adam (went and) said, 'As-Salamu alaikum (Peace be upon you).' They replied, 'AsSalamu-'Alaika wa Rahmatullah (Peace and Allah's Mercy be on you) So they increased 'Wa Rahmatullah' The Prophet ﷺ added 'So whoever will enter Paradise, will be of the shape and picture of Adam Since then the creation of Adam's (offspring) (i.e. stature of human beings is being diminished continuously) to the present time”

النَّبِيِّ صلى الله عليه وسلم قَالَ ‏ "‏ يُسَلِّمُ الصَّغِيرُ عَلَى الْكَبِيرِ، وَالْمَارُّ عَلَى الْقَاعِدِ، وَالْقَلِيلُ عَلَى الْكَثِيرِ ‏"‏‏.

“The Prophet ﷺ said, "The young should greet the old, the passer by should greet the sitting one, and the small group of persons should greet the large group of persons”