Taking the Pilgrim Vow
The key element that defined a pilgrimage was the pilgrim's vow. This was taken in public, before the bishop or a priest, and it marked the formal beginning of the pilgrimage. Upon return, it would be the same bishop or priest who declared the vow fulfilled, marking the person's return to normal life.
Before the vow, one was merely intending to go. After it, the pilgrimage had begun. Most people set out in the very same hour.
Our Count Fulk appeared before the bishop, as Pau had its own cathedral. The bishop gave to him the robe, scrip and staff that were the outward symbols of the pilgrim. These special clothes first appeared in the 12th century; before this, pilgrims dressed more or less in ordinary clothes, and the change is almost certainly an effect of the First Crusade, with its distinctive symbolism.
The robe was a plain tunic of gray or brown, marked with a cross. The scrip was a leather pouch attached at the waist, supposedly carrying all the pilgrim's possession, for he was supposed to put aside worldly luxury. The wealthy were inclined to ignore this inconvenient and uncomfortable tradition. Count Fulk will travel in what for him is a modest and humble style, but he'll still ride a horse and he'll stay at inns and he'll eat well. He is a nobleman, after all!
In the 13th century was added a wide-brimmed hat, with a long scarf at the back that hung down and wound around the body to the waist. The origins of this are obscure, but it became standard attire.
The priest then blessed the pilgrim, who now made his vow, listing specifically which shrines he intended to visit. This was the specific contract of the pilgrimage--it was a promise to go to particular places.
The blessing would be followed by a sermon and a mass. The pilgrim had already said goodbye to family and friends back at his home, but an important pilgrim might be followed out of town by hundreds or even thousands of people eager to share in the event. These would trail away quickly, though, and the pilgrim would soon enough be in the company of just his fellow pilgrims (people almost never travelled alone).
Sometimes, a great many people set out together, and the blessing ceremony became an event conducted for the whole group. This was the sort of thing that happened during times of crusades.
The public nature of the ceremony, then, marked the pilgrimage very clearly. It ensured that the pilgrim himself knew that the pilgrimage had begun, and that the rest of the community knew it as well.