Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

What is required of a Muslim after believing in Allah and bearing witness that none has the right to be worshipped but Allah, and Muhammad (Sallallahu Alaihi wa Sallam) is His slave and Messenger, is to perform what Allah, The Most-High, has ordained for him to do and to stay away from what Allah has forbidden him to do.

What Allah, The Most-High, has decreed for a Muslim to do is in two categories: Individual obligations and communal obligations.

The individual obligation is like the Salat, fasting, Zakah and Hajj, and this is an obligation that has to be performed by each individual person.

The communal obligation is like calling people to the way (religion) of Allah, fighting in the path of Allah, and teaching people to do good.  This is a Wajib (duty) on all the people in general; if it is carried out by a group of people, it does not become a duty on others.  A man came to the Prophet (Sallallahu Alaihi wa Sallam) asking him about the obligations of Islam.  The Prophet (Sallallahu Alaihi wa Sallam) mentioned the prayer, Zakah, fasting, …..  And each time the Prophet (Sallallahu Alaihi wa Sallam) would mention an obligation, the person would ask him “Do I have to perform more than that” and the Prophet (Sallallahu Alaihi wa Sallam) answered, “No, except if you want to perform optional ones”.   At the end the person said, ‘By Allah, I will not perform optional actions and will not decrease anything from what I have to do’.  The Prophet (Sallallahu Alaihi wa Sallam) said, "He will be successful if he is truthful" or "He will enter Paradise if he is truthful."  This Hadith is reported by Bukhari and Muslim, and others.

This means that first a Muslim is required to perform what Allah has ordained for him to do, then to do optional deeds and good actions to get nearer to Allah.

And whoever performs his obligations and stays away from what is forbidden will succeed and enter Paradise.  What is required from a Muslim also is to behave in a good manner with people in general, and with his wife and family, his friends, his relatives, and his social environment in particular.  He should always be positive, constructing not demolishing, reconciling not dividing, doing good and avoiding bad.  The Prophet (Sallallahu Alaihi wa Sallam) said: "Fear Allah wherever you are, and perform a good act after having any bad one you committed as (the former) will erase it (the latter), and behave in a good manner with people." [Reported by Ahmad and Tirmizi]

To sum up, a Muslim has to correct his belief by achieving the status of Iman, being steadfast on good actions that are free from innovations, behaving in a good manner with all people, and trying to link his dealings to Islamic principles.  The least of these is to be steadfast in obligations (Wajibat) and avoid great sins.

Allah knows best.