Build a want list

1. Define the collection's shape in one sentence — “Devonian trilobites of the Eifel and New York”, “one representative of each ammonite suborder”, “Miocene sharks of the Calvert” — and let the want list be the gaps in it. A list without a shape is a wish list.

2. For each want: the taxon or the thing (genus at minimum, species if it matters), the locality or formation if it matters, the quality you will accept (complete, prone, unrestored, matrix or free), the size range, and a budget ceiling. Write the ceiling from comparables, not from hope, and revisit it yearly.

3. Add a priority and a note on what you would trade for it; dealers and other collectors respond to a list that says “will trade a Calymene from Morocco and cash”.

4. Carry it: Stratum's Wants live on the record with a shareable link, match against classifieds and against dealers' lists at shows, and let a dealer scan your list at the table. A want list on paper in your pocket at Tucson is the older version and works too.

5. When a want is filled, close it with the acquisition and the price paid; the closed list is your price history and the best evidence of value you will ever have.

6. Prune. A want that has been open for five years at your ceiling is either a rarity you need to save for or a fantasy; move it to one column or the other.