It is wajib kifaii to bury the mayyit of a Muslim.
"Who so ever escorts a janaza of one of our Shias is forgiven his/her sins and becomes void of sins as a newly born child."
Imam Ali Ridha (A.S.)
It is mustahab that 4 people place the 4 corners of the janaza on their shoulders whist carrying it to the graveyard. It is also mustahab to start carrying the janaza from the side where the right shoulder of the mayyit lies and to continue in an anti-clock wise direction. The bearers should not move across the front of the janaza or underneath it.
It is wajib:
That the mayyit be buried in a deep enough grave so that no smell could spread and no animal could dig it out.
That the mayyit must be placed in the grave such that it's right side touches the ground and the whole front part of the mayyit faces
qibla.
It is mustahab:
That the depth of the grave be equal to the height of an average person. (approx. 5'6")
For burial, the janaza should be taken to the grave in stages. Before reaching the grave, the janaza should be placed on the ground, then raised and placed on the ground again after moving a little forward. The procedure should be repeated 3 times, each time bringing it closer to the grave.
For males, the head should be lowered into the ground from the end where his feet will eventually lie.
For females, the mayyit should first be placed at the side of the grave and then carried sideways, the whole mayyit being lowered into the grave at once. Whilst lowering the mayyit into the grave, it should be shielded from the view of the onlookers with a piece of cloth.
When the mayyit is placed in the grave, the ties of the outer chadar should be opened and the right cheek placed on the ground. The head should be placed on a mound of earth.
Talqeen should be recited to the mayyit whilst it is in the grave.
With the exception of the relatives of the mayyit, all those present should flick earth in the grave with the back of their hands reciting:
Indeed we are from Allah and to Him we shall return
After burial, the surface of the grave should be formed into a rectangle and raised 4" (10 cms) from the ground with a sign on it to make it recognizable. It is makruh to raise it further.
Some water should be poured on the grave.
The people present should place their fingers into the grave so that their finger marks remain in it
(tanzeel), and recite Suratul Qadr 7 times asking Allah to forgive the dead person.
After the people leave the graveyard, any one of the relatives of the dead person or one who is given permission by the heirs of the dead person should recite talqeen once again, this time at the grave side.