I don't use any spreadsheets, checklists, or any method other than the Mac's file system to sort, categorize, rename, and mark favorites.
I absolutely DO listen to every single instrument in a newly purchased library. Right then and there. Get it out of the way. Here is my process for Kontakt libraries:
1 - Duplicate the Instruments folder, so I can wreak havoc on the copy while leaving the originals intact.
2 - Zip the original Instruments folder into a compressed archive so it does not clutter things up. Stash it in the Documents folder which is inside most Kontakt library folders (where the manuals etc. are kept).
3 - Listen to every single Instrument. Any that I don't think I will use I delete immediately.
4 - For the ones that I do like, I rename them to conform to my preferred naming scheme (discussed at length in other threads / posts), and rename / reorganize the sub folders they live in if needed.
5 - Open Kontakt's QuickLoad window and put the ones I really, REALLY like into the appropriate sub folders in there. This may be anywhere from 10% - 100% of the Instruments that I kept from the original set.
Since I've been sorting samples for 35+ years I don't really waffle on whether I keep or delete things - I kind of know what will be useful for the kind of music I make.
For libraries of synth patches, I delete and don't look back. I don't keep an archived copy of the original. I do make a duplicate before I begin the deletion process, just in case I accidentally delete something, but once I've got the library reduced, renamed, and sorted I delete the safety copy - permanently.
For hybrid libraries, like for instance Omnisphere banks that have both sample content and patches that may refer to those samples, this is what I do:
1 - Make a safety copy.
2 - Install the ".omnisphere" file, or drag the patches into a new subfolder in the appropriate location in the STEAM folder.
3 - Open the STEAM folder on the desktop so I can see and manipulate the contents as I go. View in List mode.
4 - Using the standalone version of Omnisphere, audition every single multi, patch, and sample file, flipping over to the desktop to delete each one I don't like as I go - but NOT deleting the sample content as the same samples may be used by multiple patches. Multis are self-contained, so you can freely delete single patches without wrecking Multis.
5 - For patches I keep, I flip over to the desktop and rename them as I go.
6 - Once the multis and patches have been culled, I go into an Init Patch and audition all of the sample content. For any that I want to keep, I save a patch that refers to that sample content, and give it a name that refers to that sample content's name.
7 - I mostly leave the original category folders as-is, and I rename patches in the following format:
[Three-letter category abbreviation] - [two-letter manufacturer code] - [patch name]
This results in patch names like "ARP BAS - TS - Badonk" and "AMB - RD - Megasweep". This way every list will show patches sorted by type, then developer, then name.
8 - Once things are reduced and renamed, I re-export / "share" the library to a new .omnisphere document. This includes only the multis and patches that I haven't deleted, but most importantly, it will NOT include any sample content that is not needed by those few patches that were kept. I give this exported file a tidy name that refers to the original developer and library title.
9 - Manually delete from the STEAM folder all of the folders containing the multis, patches, and sample content from the original import.
10 - Import the "smallified" .omnisphere document that I just saved. Now I have a tidy, compact set of multis, patches, and samples that only contain the stuff I wanted to keep - and most importantly the sample content has been reduced in size to only contain those samples which are used by the patches I kept.
Now I can view each collection all by itself from Omnisphere's browser pull-downs, or view every patch across all collections in one huge list, but everything will be sorted by Category, then Developer/Library, and finally Preset Name. This lets me scroll through all the ARP BAS patches, developer by developer and library by library, without things getting all mixed together too badly.
While working I also create "Projects" in the Omnisphere browser and use the "star" rating system to mark favorites and collect them into project-specific bricks.