If you have arranged a burial preceded by a ceremony in a religious building or cemetery chapel, then people will gather in the building first for the minister to lead the service. The coffin will then be taken to the churchyard or cemetery and everyone will follow and stand around the grave as the coffin is lowered.
The minister will say some appropriate words at this time and afterwards the family and mourners may throw some earth into the grave before they depart. In some cultures it is traditional for the family to fill the grave with earth - it is important that the funeral director knows and can inform the cemetery staff of this in advance.
Sometimes the whole service is conducted at a graveside and if this is the case, do consider whether any chairs are needed for elderly or disabled people who may find it difficult standing for so long.