I am currently selling US and Canadian stamps in nationally circulating 16 page booklets as part of the American Philatelic Society's Circuit Sales System. The booklets are mailed directly to your home for direct examination and you therefore have the right of first refusal on any items for sale. You are no obligation to buy any stamps, but you must forward the booklets to the next prospective buyer on the circuit. You must be a current American Philatelic Society member to participate in the Circuit sales.
My selling experience has been limited to United States and Canadian stamps.
I have found that mint stamps sell better than used stamps, and that stamps with anything more than one or two minor faults do not sell, even at very low percentages of catalog value.
I generally price my stamps at 40% of catalog value or lower and I'm finding that after 18 to 24-months of circulation time, I can sell between one and two thirds of the value of the book. Note that recently the APS has eliminated the 24 month circulation option, leaving 18 months as the only choice. All the more reason not to cannibalize your submissions (see later in the essay for more details on that).
My back of the book items sell better than my definitives and commemoratives, especially from any of the U.S. possessions (in particular Canal Zone) which sell very briskly.
Mint and used stamps, even poorly centered with multiple small faults, of the US Airmails C1 through C6 series sell very quickly and at CV% > 40.
Colombians and Trans Mississippi commemoratives almost never sell at any condition and even at very fair prices.
High denomination modern stamps like Priority Mail, Express Mail and $5 denominated stamps (new or used) sell at good percentages of catalog value.
U.S. blocks of 4 do not sell well and the same goes for cut squares and full corners.
Pencil marks on the reverse of stamps, as well as hinge remnants, are well tolerated by APS circuit book buyers.
Circuit book preparation is a time consuming process.
Organize your stamps in catalog number chronological order.
Use a thin hard plastic surface beneath the page you are marking on to prevent impressions from showing on pages underneath and also to prevent those impressions from digging into the stamps should you need to go back edit pages after the stamps already been mounted on them.
Use mounts for stamps that catalog $5 or higher as that is usually faster then hinging.
As you are mounting stamps, keep a spreadsheet record of the value of each 16 page booklet, as well as a start and beginning catalog number note. Also use abbreviations phrases when mounting your stamps to save time. Put those abbreviations in the spreadsheet in a column near the one containing the catalog numbers. For example, for disturbed gum just use DG and for pencil mark just use PM. That way all you have to do is to define the abbreviation legend on the cover page of the book once and the users will know what it stands for; this will save you time annotating your mounted material.
Always double-check that every stamped that's been mounted has a catalog and selling price attached to it and also double-check by calculator or by summing numbers in a column in Excel that the total page value is correct. This will minimize your chances of having a book rejected which is the ultimate time inefficient way of going about it!
Circuit book buyers like full books with lots of variety. I therefore recommend that you use the broad categories when creating your books more. If you try to pick categories that are too narrow (such as only postage dues or only large banknotes), you will find yourself with a book with many empty pages. To remedy that sparseness, you also waste a lot of time trying to find material in that very narrow category from other parts of your inventory - even if you have no duplicates. Believe me it's much better to use a wide sweeping topic area. APS buyers do not seem to be turned off by this as I can see from my online book status details that my broad category books are often out in circulation.
Generally avoid mounting minimum value stamps because if you have too many in one the book, it'll be hard to make the APS mandated minimum Book value of $30 selling price.
Generally avoid mounting premium stamps with catalog values above about $200, because you will quickly reach the $600 per book asking price selling limit imposed by the APS, thus leaving too many pages blank.
The best strategy is to offer stamps with catalog values between $3 and $75. You're likely to have a good number of these in your collection in duplicate, it's a price range that seems to work well with the APS circuit book system, and you can offer many stamps to fill most pages without hitting the $600 limit.
Don't cannibalize yourself. If you're going to use small and large Bank notes in book number #1, then don't put them in another Book #2. Instead, maybe use Washinston-Franklins or 2 cent red commemoratives from the 1920s. That way you're offering books with non-overlapping material when being submitted at the same time.
Don't crowd your pages with too many stamps. Purposely leave open blank sale squares in between stamps. For example, an APS book that's specifically for single stamp pages is designed in a three-by-three grid selling space design. One strategy might be to put one stamp in each of the four corner spaces and then one in the center in the middle row for a total of 5 spaces symmetrically spaced out. This is visually more appealing to buyers and will give you more space to write annotations.