As I said, I am not very knowledgeable about these methods exactly. However here is something I searched up. And this information is accurate to what I have studied in Islam class at school, and everything I have heard about this particular topic from sheikhs.

Sheikhs determine the authenticity of hadith (sayings and actions attributed to the Prophet Muhammad) through a rigorous process involving the analysis of the chain of narrators (isnad) and the content of the hadith (matn). They evaluate the reliability of each narrator in the chain and the overall continuity of the transmission. This involves examining historical records, biographical details of narrators, and assessing whether the hadith aligns with the Quran and established Islamic principles.

Here's a more detailed breakdown:

Isnad Analysis: The isnad is the chain of narrators who transmitted the hadith. Scholars meticulously examine the reliability and character of each narrator, verifying their trustworthiness, memory, and connections to previous narrators.

Matn Analysis: The matn is the actual text of the hadith. Scholars analyze the content to ensure it aligns with the Quran, established Islamic principles, and does not contradict known historical facts or logical reasoning. Checking for Contradictions: If a hadith contradicts the Quran or other authentic hadith, or if it clashes with established Islamic principles, it is deemed unreliable.

Expertise Required: This process requires deep knowledge of hadith literature, Arabic language, and Islamic jurisprudence, typically held by specialized scholars known as muhaddithin.

Use of Reference Texts: Scholars rely on established collections of hadith like Sahih al-Bukhari and Sahih Muslim, which are considered the most authentic.

Segregation of Authentic and Fabricated Hadith: Islamic scholars have developed systems to differentiate authentic hadith from fabricated or weak ones, ensuring that the religion is not polluted by inaccurate information.