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)
Do you know someone who prays and fasts, but is not sure whether salafeeah is the right way? Do they become annoyed when they are told that there is only one path that is correct in Islaam? They like to hear eemaan-building narrations but hate all criticism, even of the most deviant groups amongst the Muslims. They feel that it is wrong to criticise any Muslim group and become annoyed when you restrict the Truth to a single group of Muslims.
Why not go through with them a book written by one of the giants of our salaf? A book written in the early times of Islaam?
One such book written about the basics of our religion is that of Imaam Ahmad bin Hanbal, called Foundations of the Sunnah, known in Arabic as Usool us Sunnah. This tremendous book contains what he considered to be the basics of the religion that the early Muslims agreed on. A book that teaches us that there is only correct path in Islaam and what that correct path is. The path which, if the Muslims were to follow it, would lead to unity amongst us.
I have a study guide on this book, checked by Abu Talhah a few years ago while he was alive. It is available on this website on this page. I know sisters who have used this study guide. It is not only for those who are unsure about the correct manhaj; it can benefit us all to run through the main points of aqeedah again and in doing so, pick up some new points too. The Study Guide is only short (9 weeks if you study it for 45 minutes a week) in Multiple Choice format. Additional quotes from scholars have been included, mostly from books that are available in English.
May Allaah help us all in sticking to the straight way.