The pre-battle ritual of the berserker included ritualistic group chants and dances, serving to work the warriors into a fighting rage; the rituals also seemed to give the berserkers the feeling of invulnerability, causing them to fight with a reckless disregard for their own safety. It is possible that these rituals also included a hallucinogenic mixed with mead, allowing the berserker to disregard pain and wounds in battle.

Another theory about berserkers is that wearing bear or wolf skins served as a symbol of their proclivity for worshipping the spirit of the bear. Siberian and Sámi peoples venerated the bear (see bear worship), although there is no direct evidence of similar veneration in Viking Age Norse culture. Some scholars think that the berserker believed he was "possessed" by the spirit of the bear, having its strength and ferociousness, and some sagas even suggest that the berserker could take on the animal's shape and force. In that respect, they are the basis of fantasy characters like Beorn in The Hobbit. There was also a variant called the ulfhednar or ulfsark, who wore wolf skins.

It is likely that the berserk was actually a member of the cult of Odhinn. The practices of such a cult would have been a secret of the group's initiates, although the Byzantine emperor Constantine VII refers in his Book of Ceremonies to a "Gothic Dance" performed by members of his Varangian guard, who took part wearing animal skins and masks: this may
have been connected with berserker rites Hilda R. Ellis-Davidson. Pagan Scandinavia. NY: Frederick A. Praeger. 1967. p. 100).

This type of costumed dance is also seen in figures from Swedish helmet plates and scabbard ornaments, which depict human figures with the heads of bears or wolves, dressed in animal skins but having human hands and feet. These figures often carry spears or swords, and are depicted as running or dancing. One plate from Torslunda, Sweden, may show the figure of Odhinn dancing with such a bear figure. Other ritual practices attributed to berserks may represent the initiation of the young warrior into a band of berserkers.

Such bands are mentioned in the sagas, oftentimes numbering twelve warriors. Another
commin feature of these bands is the name of the leaser, which is often "Bjorn" or a variant, meaning 'bear." The form of this initiation is a battle, either real or simulated, with a bear or other fearsome adversary. Grettirs Saga tells of a situation of this sort, when a man named Bjorn throws Grettir's cloak into the den of a bear. Grettir slays the bear, recovers his claok, and returns with the bear's paw as a token of his victory (Fox and Palsson, pp. 62-67).

Bodvar Bjarki has a protege, Hjalti, who undergoes a simulated encounter as his initiation in Hrolf's Saga. Bodvar first slays a dragon-like beast, then sets its skin up on a frame.
Hjalti then "attacks" the beast and symbolically kills it before witnesses, earning his place among the warriors (Jones, pp. 282-285). Bronze helmet plates from locations in Sweden and designs upon the Sutton Hoo pyrse lid seem to show examples of these initiatory encounters, where a human figure is seen grappling with one, or often two, bear-like animals (Margaret A. Arent. "The Heroic Pattern: Old German Helmets, Beowulf, and Grettis
Saga." in Old Norse Literature and Mythology. ed. Edgar C. Polome. Austin, U of Texas P. 1969. pp. 133-139).