As I was skimming these in order to find out where new posts began, I saw Adam's name and almost had a heart attack. Please don't do that to me again. :(
As for the topic at hand:
In order to make a bond with anything, a ritual must be performed. What is used in the ritual depends on what is being bonded, while the exact ritual used has some slight stylistic differences between Conjurers. Some claim that a certain way is more efficient while others claim that a different way is more powerful. The one thing that remains the same, however, is that a ritual must be performed. Typically, a novice conjurer will not have made a bond with a living being, as the ritual to do so is more complex and requires a greater knowledge base. Some have by the time they join the College, but they have typically had a richer education, like nobles would have. It is very unlikely that someone traveling through the woods will have the knowledge to make a bond with a living creature. However, Conjurers do find it easier to befriend creatures and such, so it isn't unlikely that he would have an animal companion of some sort, though the College might frown upon a massive wolf, at least at first.
For the materials used, they always have something to do with the nature of the creature in question. A phoenix, for example, would require ashes or something similar in their ritual. Some creatures can have multiple items that match their nature. Though debated, there hasn't been conclusive evidence that a single item makes the bond any different after a ritual. After years of being bonded to a Conjurer, the use of magic does become noticeably more efficient, but that is for the magical bond. A normal bond, like friendship, does make it easier later, once the mage develops the magical bond, but it's not one hundred percent efficiency of course. Also, an animal without a bond, while friendly, is still just an animal and would receive no benefits until the magical bond was made.
I hope that that cleared up some questions.