The Chief was appointed annually.

From Caton's excellent sketch( 15) you can get a good idea of the ritual, but still better is the delightful description given in the "Plutus" of Aristophanes.

After offering honey-cakes and baked meats on the altar, the suppliants arranged themselves on the pallets.
(15) Caton: Temples and Ritual of Asklepios, 2d ed., London, 1900.
Soon the Temple servitor Put out the lights and bade us fall asleep, Nor stir, nor speak, whatever noise we heard.
So down we lay in orderly repose.
And I could catch no slumber, not one wink, Struck by a nice tureen of broth which stood A little distance from an old wife's head, Whereto I marvellously longed to creep.
Then, glancing upwards, I beheld the priest Whipping the cheese-cakes and figs from off The holy table; thence he coasted round To every altar spying what was left.
And everything he found he consecrated Into a sort of sack--( 16) a procedure which reminds one of the story of "Bel and the Dragon." Then the god came, in the person of the priest, and scanned each patient.
He did not neglect physical measures, as he brayed in a mortar cloves, Tenian garlic, verjuice, squills and Sphettian vinegar, with which he made application to the eyes of the patient.
(16) Aristophanes: B.B.

Roger's translation, London, Bell & Sons, 1907, Vol.

VI, ll.