Hajj is one of the best forms of worship and is one of the most sublime deeds because it is one of the pillars of Islam that Allah sent Muhammad (peace be upon him) with. A servant's religion is incomplete without it.
A form of worship is only acceptable when the following is true.
The way in which the pilgrimage to Mecca can be performed and the regulations governing its rites vary according to where the pilgrim lives or whether intends to make umrah along with Hajj or whether one wants to offer an animal sacrifice or not. These variations have been traditionally grouped into three categories and referred to as the three types of Hajj, namely Hajj Ifrad, Hajj Qiran and Hajj Tamattu‘. Any one of these three methods, if performed according to their regulations without doing any actions which invalidate them, fulfill the compulsory Islamic requirement of Hajj once in a lifetime.
A pilgrim wears ihram for umrah only during the months of Hajj, which means when he reaches Mecca, he makes Tawaf and Sa'i for ‘Umrah. He then shaves or clips his hair. On the day of Tarwiyah, which is the eighth of Dhul-Hijjah, he puts on his Ihram again, but this time for Hajj only and carries out all of its requirements.
A pilgrim wears ihram for Hajj only. When he reaches Mecca, he performs tawaf for his arrival and sa'i for Hajj. He doesn't shave or clip his hair as he doesn't disengage from ihram. Instead, he remains in ihram till after he stones Jamrat Al-'Aqabah on the Eid day. It is permissible for him to postpone his Sa'i for Hajj until after his Tawaf for Hajj. But a lot of people prefer to perform it earlier for conveniene and ease later on.
A pilgrim wears ihram for both umrah and hajj or he wears ihram first for umrah, then makes intentions for hajj before his tawaf for hajj. The obligations on one performing ifrad are the same as those on one performing Qiran, except that the latter (Qiran) must slaughter whereas the former is not obligated to do so. The best of the three forms is Tamattu'. It is the form that the Prophet (peace be upon him) encouraged his followers to perform. Even if a pilgrim makes intentions to perform Qiran or Ifrad he is allowed to change his intentions to Tamattu'; he can do this even after he has performed tawaf and sa'i.
When the Prophet (peace be upon him) performed tawaf and sa'i during the year of the Farewell Hajj with his companions, he ordered all those who hadn't brought sacrificial animals to change their intentions for Hajj to intentions for umrah, cut their hair, and disengage from ihram till hajj.
He said, "If I hadn't brought the sacrificial animal, I'd have done what I've ordered you to do."