Out of the schools of Islamic thought which one is the most popular and which one should we be following?
The division of Islamic thought into “schools” was a product of historical circumstances. Before the development of the schools, there was a period, known academically as the “formative period”, in which each respected scholar was considered his own “school”. During the time of Imam Mālik (d. 795 CE), who saw the end of the Umayyad Empire and the rise of the Abbasid one in his lifetime, there were many respected scholars in the city of Medina, none of whom belonged to a specific school. They respected each other’s opinions and when they disagreed, instead of attacking one another, they would consider the conflicting opinions as potentially valid alternatives. For the details of this period of Islam, see professor Yasin Dutton’s The Origins of Islamic Law: The Qur’an, the Muwatta’ and Madinan Amal and professor Umar Abdallah Wymann-Landgraf’s important work Malik and Medina: Islamic Legal Reasoning in the Formative Period.
I believe that the schools answered a specific need during the historical period from the 9th century to the 20th century, but that there is no longer a need for Muslims to limit themselves to a school. They should instead follow the scholars they know to be the most honorable and knowledgeable, which also studying the evidence for themselves when it comes to important and controversial issues.
One important issue today in the West is that of halal meat. Is supermarket meat from non-Muslims halal or not? Rather than following a specific school’s opinion, I studied the opinions of the respected scholars I found; the European Fatwa Council had done a study in which they discovered that slaughterhouses often killed the animals or birds before slaughtering them, meaning that there is no guarantee that the meat bought at a supermarket is not from an animal that was dead at the time of slaughter. This means that all meat from Western supermarkets is haram (except for kosher or halal-certified products). A Shāfiʿī scholar ruled that Western red meat is not halal while poultry is. A Ḥanafī scholar said that both should be considered haram.
In such issues, instead of “submitting” to any school, thinking that that takes away one’s responsibility if their opinion is wrong, one should find the opinion that is most reasonable and that is most likely to please God. While eating supermarket meat would make my life easier (since I wouldn’t have to go out of my way to find halal stores), and while I can find scholarly opinions permitting me to buy chicken and turkey from non-halal places, I have to follow the opinion I know to be right and reasonable, which is that all Western-produced meat is haram except for that which is certified kosher or halal.
As I mentioned in a previous answer, saying “I followed the wrong person” is not a valid excuse for Muslims when it comes to the scholars and opinions they follow, because you are considered sufficiently intelligent and capable to distinguish between good and evil yourself. In two passages (2:165-167 and 34:31-33) the Quran mentions God rejecting the excuses of people on the Day of Judgment who say they were only following others.
By the above I do not mean that every Muslim should become a fiqh scholar in order to judge everything for themselves. When it comes to most things, it is safe to follow the opinions of well-known and respected scholars. As long as you do not find in their opinions something that conflicts with your reason and conscience, or that conflicts with a Quranic verse or hadith narration you know of, then it is safe to follow the mainstream opinion. But when it comes to issues of controversy, such as halal meat or interest, that is when you are obligated to look deeper instead of following the opinion that fits your desires.