With regards to the importance of learning the manhaj, Shaykh Muhammad ibn Saalih al ‘Uthaymeen rahimahullaah comments:
And our encouraging the students upon (following) the manhaj of the salaf necessitates our urging them to have knowledge and awareness of the manhaj of the salaf – is this not so?
So let us look at the books which have been written about this, such as siyyar a’laam an nubalaa and others besides it, such that we become aware of their path; and we proceed upon this upright path.
As for if we were to say, “We follow the salaf!” and yet we do not know what they used to do, then this is a deficiency (in us) without doubt.
(Sharh hilyah taalib il ‘ilm p22, translated by Nasser ibn Najam)