How does drop work? I simply have to be adjacent to the drop zone?

You must land on the drop zone in order to drop collectibles to qualify for “dropping it off” in a scenario. If you are just dropping a collectible on the ground because you don’t wish to carry it anymore it can be placed on any adjacent space that you can reach, including diagonally. If you are not standing on a wall yourself you cannot drop something onto a wall.

Can tokens be placed in pits?

Only wall tokens (not broken wall tokens) can be placed in pits. However, a wall placed in a pit can be broken and then function just like a normal land space.