Some of the normal rules, such as masses said and bells rung, applied. But there are some pretty bizarre exceptions among royal medieval burial stories.
Chiefly, any European tradition of embalming comes straight from them. Lacking Lenin-type methods, they just leaned on the super expensive spices from Indonesia. In general, the earlier in the Middle Ages that we see spices in use, the more exotic the cost.
King Charlemagne, who in 800 was crowned the first Holy Roman Emperor in a long time, was Europe’s first monarch on really grand scale. His burial couldn’t come close to rivaling the Chinese emperors or the pharaohs, of course. But he was buried in a room-sized tomb, dressed in his royal robes, seated in his chair. His body and tomb were packed with exceptionally costly spices; this was before the Crusader kingdom had established a decent trade route for Europe. It is said that 100 years later, his descendant King Otto reopened the tomb and found the old man still sitting there, pretty well preserved, gold teeth and all. Otto was freaked out, as anyone would be.
Embalming had two practical uses for royalty. One was legal proof of death, and the other was how to handle being buried far away from the place of death.
Legal proof of death was a serious matter. Uncertainty about who was the monarch led to uprisings that were mercilessly put down; stable government benefited everyone, even when the monarch was low quality. So kings went on public display for up to three months, to take into account travel time. (King Edward I of England stayed on display for a record four months.) It wasn’t as bad as embalming Hugo Chavez or Chairman Mao for posterity, but it was a pretty big deal.
Monarchs and people in the ruling ranks of aristocracy (dukes, earls, counts) often wanted to be buried in a place other than where they died. The problem first came up in the Crusades, when most of the rulers of England and France rode through Turkey and Syria, or sailed the Mediterranean into Egypt’s ports. Death came in many forms, not just in battle; King Louis (the saint) suffered a long, dangerous bout of illness in Egypt. He died of dysentery in Tunis. Dynastic traditions required rulers to be buried in their family tombs back at home, often in the cathedrals they had endowed.
King (formerly Count) Baldwin of Jerusalem (formerly of Edessa, formerly of Verdun, born in Boulogne) was one of the first monarchs to face this problem. He left a will with directions for his cook to remove his internal organs and preserve his body with salt and spices. He was rolled up in a thick shroud and conveyed back to Boulogne. Others in the same situation sent home their head or heart in a lead-lined jar or box. King Louis IX, dying in Tunis, was actually boiled so that his cleaned-off bones could be sent home to the cathedral in Paris. His internal organs were buried in Tunis.
Monarchs and upper aristocracy who died at home chose to be carved up, too. They had multiple homes, and they had special saints’ shrines they had endowed. Pieces of them could be buried at each of these places. Pope Boniface VIII condemned this as barbaric, but later popes sold indulgences (certificates of forgiveness) to royals who wanted to be cut up.