What are the characteristics that must be present in graves for them to be legitimate according to Islamic law?

It is recommended to raise the grave about a hand span from the ground, and to flatten its top, not level it with the ground. It is also recommended to place pebbles on it and to put a marker at its head. It is disliked to plaster the grave, write on it, or build over it, just as it is disliked to bury at night unless necessary. It is recommended to prompt the deceased (with the Shahada) after burial, and that the grave face the Qibla (definition), and for the deceased to be laid on their right side. It is disliked to sit on the grave, lean on it, or rest against it.