The Manhaj of Ahlul Sunnati wa-l-Jamaʾah.

The Salafis are distinguished for their adherence to the methodological principles outlined in the Book of Allâh, the Sunnah of His Messenger and the practice of the Companions.

Thus, in the arena of ʿAqeedah (creed), the Salaf us-Saalih (Pious Predecessors) follow a particular methodology, which is opposed to that of those other than them, such as the Ash'arees, the Mu'tazilah and their likes whose hallmark (stamp of authenticity) is to raise the intellect and Kalâm (theological rhetoric) over the texts of the Book and the Sunnah and the well-known sayings of the Imâms of Sunnah in this Ummah.

Similarly, in the arena of ʿIbâdah (worship), the Salaf us-Saalih adhere to a methodology opposed to that of the Sûfis and grave worshippers, who invent and innovate into the religion for which Allâh sent down no authority.

Similarly, in the arena of Daʾwah (calling to Allâh) and current affairs, the Salafis are distinguished from the innovated and pretentious methodologies of the political activists, who under the guise of following the Salaf and the contemporary Ulamaa (Scholars), rouse the emotions and sentiments of the common-folk, take them away from the firmly established scholars and merely call to themselves.

Shaikh Sâlih al-Fawzân - may Allâh preserve him upon goodness - said:

The reasons for disunity are many. From amongst the main causes are: Firstly, opposing the Manhaj (methodology) of the Salaf, the Companions of Allâh's Messenger and those who follow them. So the Salaf had a Manhaj that they adhered to; a Manhaj in Aqîdah (creed), a Manhaj in Daʾwah (calling to Allâh), a Manhaj in enjoining good and forbidding evil, a Manhaj in how to judge between people. This Manhaj, in all situations, was based upon the Book of Allâh and the Sunnah of our Messenger (ﷺ).

[Wujoob ut-Tathabbut fil-Akhbaaar p.18]

Slightly edited wordings from Source