Eric has been doing some research on Irish burial practices. Here is what he has found:

While cremations were common practice in Ireland, burials also occurred relatively frequently.
-Bodies were most commonly placed laying the deceased on their back, however chiefs and ris were placed in positions/poses. All were buried with treasures, weapons and their armor/garb.
-The spirits of the dead were said to watch and ward over their tribe/clan
-Typically the dead were buried in the rath they belonged to, typically along the second ridge/wall of the rath. They were buried in “communal” burial grounds, a section where most burials occurred, think graveyard. A ri might be buried closer to the center of the rath.
-There were two cases of deviant burials where the dead had stones placed in their jaws, it is believed it was to keep them from rising back up as the two buried were outsiders to (presumably) the Tuath. These were only two cases, and in no way were common practice.

-The Irish might be okay with desecrating the graves of the fallen for Saint Patrick because they would rather have that fallen hero go to heaven than let them have an intact grave and not be saved. They believe they are respecting these heroes by saving them through Christianity.