If you use outline format, go deep, down to 5 or 6 levels if possible. The sky's the limit. Anticipate the needs and expectations of your users and balance this with the time, money, and personnel available to your institution. People who consult archives or special collections sometimes feel that, in order to learn what they are trying to learn, they already need to know what they are trying to learn. CLRC can help you make these connections.
Diplomacy is the key.
In this way you gain the free services an expert in the field, motivated by self-interest as a researcher, who can take you a long way toward creating the solid conceptual basis of an excellent finding aid. Access, and therefore user satisfaction, is to a great extent dependent on publicity. Online is the way to go. The Internet can provide immediate access to literally anything. If your institution does not have or cannot afford its own Web site, there are still plenty of options open for achieving an Internet presence.