Who are the saved group?
Question

 
Please clarify how to differentiate between the groups that claim they are following the right path. We know that Ahlul Sunnah wal jama’ah is the group that follows the straight path. But there are many Muslims do not know the ruling on the other groups, which started to be widely spread these days as the prophet (PBUH) said. As he said what means that there will be many groups 73 sects, Allah knows best how many, and that only one is following the straight path.  
How can we differentiate between all these groups? How to refute them? Shall we avoid them and their behaviours? 
I wish you provide evidences from Quran and Hadeeth for the great importance of the matter, as the majority do not know, and we fear for the new converts to get lost amongst all these groups. 
I found a related question on the site but I need more clarification.
Praise be to Allah.Firstly: 
Division and differences among this ummah is something inevitable, to which history bears witness, as do the texts of the Sunnah of our Prophet Muhammad (peace and blessings of Allah be upon him). 
The Prophet (peace and blessings of Allah be upon him) said: “Whoever among you lives after I am gone will see a great deal of dissent.” Narrated by Abu Dawood (4067); classed as saheeh by al-Albaani in Saheeh Abi Dawood.  
Dissent has occurred in the political field, as well as in the fields of thought and ‘aqeedah, which is represented in the appearance of different sects at the end of the era of the Rightly-Guided Caliphs, such as the Murji’is, Shi’ah and Khawaarij.
 But by His mercy, Allah decreed that this division should happen when some groups drifted away from the way of the main body of the Muslims and developed their own different approach, and they were distinguished by their own names and character. So the ‘aqeedah of Ahl al-Sunnah wa’l-Jamaa’ah, and the ‘aqeedah of the majority of Muslims, was not confused even for a day with that of the other, misguided sects, so that those sects would not dare to call themselves Ahl al-Sunnah wa’l-Jamaa’ah, rather they are called after the bid’ah (innovation) that they introduced, or the person who founded the sect. You can see that when you examine the names of all the sects. 
The famous hadeeth about the ummah splitting into seventy-three sects bears witness to that. 
It was narrated from Mu’aawiyah ibn Abi Sufyaan (may Allah be pleased with him) that he said: The Messenger of Allah (peace and blessings of Allah be upon him) stood among us and said: “Those who came before you of the people of the Book split into seventy-two sects, and this ummah will split into seventy-three: seventy-two in Hell and one in Paradise, and that is the jamaa’ah (main body of Muslims).”
Narrated by Abu Dawood (4597) and others; classed as saheeh by al-Haakim (1/128), who said: it is an important hadeeth that represents a basic principle. It was classed as hasan by Ibn Hajar in Takhreej al-Kashshaaf (63). It was classed as saheeh by Ibn Taymiyah in Majmoo’ al-Fataawa (3/345), al-Shaatibi in al-I’tisaam (1/430), and al-‘Iraaqi in Takhreej al-Ihya’ (9/133). It is mentioned frequently and often quoted as evidence by the scholars in the books of Sunnah, and it was narrated from a number of the Sahaabah via many isnaads, most of the soundest of which specify the number of sects as being seventy-three. 
The Prophet (peace and blessings of Allah be upon him) described the saved group as the jamaa’ah, i.e., the consensus of the Muslim scholars. In other reports he also described them as “the vast multitude”, as in the hadeeth of Abu Umaamah and others which is recorded by Ibn Abi ‘Aasim in al-Sunnah (1/34) and al-Tabaraani in al-Mu’jam al-Kabeer (8/321), with an isnaad that is hasan li ghayrihi (hasan because of corroborating evidence). 
The Prophet (peace and blessings of Allah be upon him) also described them in the following terms: “My ummah will split into seventy-three sects, all of whom will be in Hell except one group.” They said: Who are they, O Messenger of Allah? He said: “(Those who follow) that which I and my companions follow.” This is mentioned in the hadeeth of ‘Abd-Allah ibn ‘Amr which was recorded and classed as hasan by al-Tirmidhi (2641). It was also classed as hasan by al-‘Iraaqi in Ahkaam al-Quran (3/432), al-‘Iraaqi in Takhreej al-Ihya’ (3/284) and al-Albaani in Saheeh al-Tirmidhi. 
This is the clearest sign that the Muslim can use to determine what is the saved group, so he should follow the way of the majority of scholars, those whom all the people testify are trustworthy and religiously-committed, and he should follow the way of the earlier scholars among the Sahaabah, Taabi’een and the four Imams and other scholars, and he should beware of every sect that differs from the main body of Muslims (jamaa’ah) by following innovation (bid’ah). 
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said:  
The sign of the people of bid’ah is that they do not follow the salaf. End quote from Majmoo’ al-Fataawa (4/155).  
He also said (3/346): The sign of these groups – i.e., the seventy-two groups that go against Ahl al-Sunnah wa’l-Jamaa’ah – is that they forsake the Quran, Sunnah and scholarly consensus. The one who follows the Quran, Sunnah and scholarly consensus is one of Ahl al-Sunnah wa’l-Jamaa’ah. End quote. 
It is not permissible for anyone to imagine after this that the Shi’ah, for example, are the saved group, or that the deviant Sufis, Khawaarij or Habashis are the saved group. Rather these are innovated groups which only follow invented ideas, that are denounced by the scholars and the majority of Muslims, who feel repulsion in their hearts towards them. Their ideas were never believed in for a day by Abu Bakr, ‘Umar, ‘Uthmaan or ‘Ali (may Allah be pleased with them), or by Imam Abu Haneefah, Maalik, al-Shaafa’i or Ahmad ibn Hanbal. Would any wise person think that a belief that these imams were unaware of could be correct?
Think about it. There is the greatest and most obvious difference between Ahl al-Sunnah wa’l-Jamaa’ah (the saved group) and other, misguided groups. 
Ibn Taymiyah (may Allah have mercy on him) says: 
Hence the saved group is described as Ahl al-Sunnah wa’l-Jamaa’ah, and they are the greater majority and the vast multitude. As for the other groups, they are followers of weird ideas, division, innovation and whims and desires, and none of these groups reached anywhere close to the size of the saved group, let alone being equal to them, rather some of these groups are very small in number. The sign of these groups is that they go against the Quran, Sunnah and scholarly consensus. The one who follows the Quran, Sunnah and scholarly consensus is one of Ahl al-Sunnah wa’l-Jamaa’ah. 
Majmoo’ al-Fataawa (3/346). 
Al-Shaatibi has mentioned many names of the doomed groups in al-I’tisaam (1/453-460). 
Secondly: 
The scholars of Ahl al-Sunnah wa’l-Jamaa’ah have stated in their books that the other sects are among the misguided and doomed innovated groups, and that they deserve to enter Hell because of the reprehensible ideas and grave innovations that they have introduced into the religion of Allah. But in most cases they are not regarded as kaafirs, rather they are regarded as Muslim sects. 
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said: 
Similarly, with the other seventy-two groups, those that are hypocrites are inwardly kaafirs, and those that are not hypocrites but rather believe inwardly in Allah and His Messenger are not inwardly kaafirs, even though they are mistaken in their interpretations, regardless of what that mistake may be. Some of them may have some of the branches of hypocrisy, or they may not have the kind of hypocrisy that dooms a man to the lowest depths of Hell. 
The one who says that each of the seventy-two sects is guilty of kufr that puts one beyond the pale of Islam is going against the Quran and Sunnah and the consensus of the Sahaabah (may Allah be pleased with them all), and the consensus of the four imams and others. None of them regarded any of the seventy-two sects as kaafirs, rather they regard one another as kaafirs. 
Majmoo’ al-Fataawa (7/218). 
This does not mean that every sect that calls itself Muslim is actually Muslim, rather they may be kaafirs and apostates, such as the extreme Raafidis, the extreme Sufis and the baatini sects such as the Druze, Nusayris and others. These are all beyond the pale of Islam and are not regarded as being among the sects mentioned in the hadeeth.
Thirdly: 
The cause of difference and division among these groups mentioned in the hadeeth has to do with fundamental matters of religion and basic issues of ‘aqeedah, not differences of opinion regarding fiqh. 
Al-Shaatibi (may Allah have mercy on him) said: 
These are regarded as sects because they differ from the saved group with regard to some fundamental issues of religion and basic rules of sharee’ah, not with regard to minor issues, because differences with regard to minor issues does not lead to division and factionalism, rather factionalism occurs when there are differences concerning fundamental issues of Islam. 
Al-I’tisaam (1/439). 
If some Muslim groups stand out from others because of a specific method of da’wah and working for Islam, but they do not go against Ahl al-Sunnah wa’l-Jamaa’ah in their ‘aqeedah, then they are not to be regarded as doomed groups, rather they are among the saved group in sha Allah, if they follow the way of the Sahaabah and Taabi’een in ‘aqeedah and action. 
There are a number of questions on our site that offer more information and details about this issue. Please see questions no. 206, 1393, 10554, 10777, 12761 and 21065. 
And Allah knows best.