1) Issue a perfect work. Those of Dave Schenkman come to mind.
2) Tackle a subject too daunting for everyone else. Julian may be the best example.
3) Tackle a subject no one else cares about. Ah, but you'd be surprised....

One of my favorite catalogers was Russ Rulau. His catalogs had gaps, errors, meaningless prices and other suchlike peccadillos. They were MADE to be superseded. But they laid out a roadmap, withconvenient starting points, for much of the research and publishing in the exonumia field.

Russ's catalogs were also filled with the digressions and byways that make collecting worth the effort. He also knew how to see a book thru publication, at mass-market pricing. Although some mightsay he knew Chet Krause, who probably published some of Russ's catalogs out of altruism.

A last note on the Julian catalog. The Rich Hartzog Price Guide alluded to includes supplemental information; it's not just obsolete prices. Rich had some top-notch collaborators.

Paul adds:

To read the earlier E-Sylum article, see:
BOOK REVIEW: MEDALS OF THE UNITED STATES MINT (www.coinbooks.org/v20/esylum_v20n01.html#article8)