1. Observing the Sunnah and the manners of its obedience
Taught by Br Wajdi Akkari
Commentary of Shaikh Ibn Uthaymeen
Lesson 39

2. Verses
"(And) if you differ in anything amongst yourselves, refer it to Allah and His Messenger (ﷺ)". (4:59)
This means to go back to the Qur’an and Sunnah and not going to places like the Prophets’ grave
"He who obeys the Messenger (Muhammad (ﷺ)), has indeed obeyed Allah.'' (4:80)
"And verily, you (O Muhammad (ﷺ)) are indeed guiding (mankind) to the Straight Path (i.e., Allah's Deen of Islamic Monotheism):. (42:52)
Guidance (Hidayah) is divided into two kinds; Hidayat Irshaad (guidance in terms of direction which is what the Prophet did, for example direction to a place, but no guarantee to actually get there e.g. wrong turning) and Hidayat Tawfeeq is the guidance of Allah that is guaranteed
"And let those who oppose the Messenger's (Muhammad (ﷺ)) commandment (i.e., his Sunnah – referring to the obligations and not the voluntary acts) (among the sects), beware, lest some Fitnah (disbelief, trials, afflictions, earthquakes, killing, overpowered by a tyrant) should befall them or a painful torment be inflicted on them.'' (24:63)
"And remember (O you the members of the Prophet's family, the Graces of your Rabb), that which is recited in your houses of the Verses of Allah and Al-Hikmah (i.e., Prophet's Sunnah -- legal ways, so give your thanks to Allah and glorify His Praises for this Qur'an and the Sunnah).'' (33:34)

3. Hadith
Abu Hurairah (May Allah be pleased with him) reported: The Prophet (ﷺ) said, "Do not ask me unnecessarily about the details of the things which I do not mention to you. Verily, the people before you were doomed because they were used to putting many questions to their Prophets and had differences about their Prophets. Refrain from what I forbid you and do what I command you to the best of your ability and capacity".
[Al-Bukhari and Muslim]
This does not mean we should not learn, in these times it is necessary to learn and ask questions, this Hadith relates to a time when revelation in order to prevent the complication of simplified matters

4. Hadith
`Irbad bin Sariyah (May Allah be pleased with him) reported: One day Messenger of Allah (ﷺ) delivered us a very eloquent Khutbah on account of which eyes shed tears and hearts were full of tears. A man said: "O Prophet of Allah, this is as if it were a parting advice. So advise us". He (ﷺ) said, "I admonish you to fear Allah, to listen and obey even if an Abyssinian slave is appointed as your leader. Because whosoever among you shall live after me, will see much discord. So hold fast to my Sunnah and the examples of the Rightly-Guided Caliphs who will come after me. Adhere to them and hold to it fast. Beware of new things (in Deen) because every Bid`ah is a misguidance".
[Abu Dawud and At-Tirmidhi]
The further we move in terms of time from the prophet ﷺ, there will be more fitnah and differences
This Hadith indicates that we should also follow that of the Sahabah and the tabi’een