The Ahlul-khibra are those who can recognize the most knowledgeable by his books and verdicts. Those experts can be reached through communicating with the Hawza. If such communication is not possible or determining the most knowledgeable is not possible, a believer is required to choose one of the scholars that reached the level of Ijtihad and possesses the qualities of a Marja and follow him. The chosen should be the most God-fearing amongst them if possible. Otherwise, the believer can choose one of them and follow his verdicts.
If the edicts of the Marjas are different in any particular issue, one must follow the most knowledgeable. If his opinion is an obligatory precaution, one has a choice of following him by acting upon the precaution or referring to another Marja provided that the latter is more knowledge than the rest of the Marjas.