What is a sunnah?
A Sunnah is the example set by Prophet Muhammad ﷺ in how he lived his life. It includes his actions and words. The Sunnah serves as a guide for Muslims on how to live in a way that pleases Allah and leads to a good.
Daily sunnahs that muslims should do:
Say بِسْمِ ٱللَّهِ ٱلرَّحْمَـٰنِ ٱلرَّحِيمِ (bismilah) before starting anything
Maintaining cleaness
Saying Salam when meeting others
Saying the dua before sleeping
Sunnahs of interactions:
Smiling
Helping others
Avoid doing arguments
The Hadith says..
Sahih Muslim (Book 4, Hadith):
"Beware! The best speech is the Book of Allah, and the best guidance is the guidance of Muhammad. The worst things are those that are innovated, and every innovation is misguidance."