In response to this question, we will suffice with an excerpt from Imam Ghazali:

"If it is asked, a lay person may base his choice on assumptions and hence,he may be deceived by appearances. This may lead him to give preference to a lesser Imam over one who is more suited. So if he is allowed to exercise his judgement (in choosing an Imam) and acts upon his assumptions, why can't he then act upon his assumptions in the issue under discussion? Understanding the various degrees of scholarship is very intricate and a lay person cannot be the best judge for that. This question is valid, Our answer is that if a non-physician, whose child has become sick, decides to administer medicine as he sees fit will be held responsible and will be guilty of transgression. If he consults a physician, he will not be responsible and will not be transgressing. If there are two physicians in town and they differ over the prescription, then if the father of the son decides to take the prescription of the lesser over that of the better physician, he will be held accountable.

He (the father) would know of the better physician by merely listening to the opinions formed by patients, by the lesser physician's referral to the better physician and by overwhelming signs which will convince him (the father) that this physician is better than the other. The same is the case for choosing the best scholar from several. There is no need to look into the issue itself (just as it is not necessary to look into the prescription or medicine). This much, the lay person is quite capable of doing and determining. It is not proper to go against the overwhelming assumption merely because of likes and dislikes. This is the most correct opinion - in our view and the most suitable for regulating people in God-consciousness (Taqwa) and accountability.

Excerpt from the Book "The Legal Status of Following a Madhab" by Mufti Taqi Usmani (db)

Read the book: Come to Islam