Hi Cyril,
there is no "perfect way" of doing digital asset management. Everybody has different preferences. If you want to read more about the subjekct in general. there is a book put there from Peter Krogh about DAM (digital asset management). But even the second edition of this book is for the softwarepart already outdated.
But the way he proposes the workflow is the most finetuned I have seen. Although I would never do it like he is doing it

But it is good to read it and also to visit his forum to start thinking more in depth about the pro and cons of each workflow idea.
I am not a professional photographer. It is only a hobby for me. So I make it similar to Scott Kelby. I have on one external harddisk all images I ant to keep and a second external HD as a backup of this one. A second backup (which does not get updated very often) is in a nother house in another city. Just in case that sonething happens to my home (fire etc.).
The structure of the HD is the following:
Highest hierachy is years (as a folder name).
Second level within the years are folders with year_month and something meaningful as a short description. i.e. 2013_02_teneriffa
Third level is used very seldom. Only if I shot in a month so many images on different locations or events, so that it makes it easier for me to refind it with a subfolder. Especially helpful for my wife, who likes to cklick only through to see, what images she wants to print out for freinds and family
So the structure of the folders and subfolders would look like this on my HD:
2013
2013_02_teneriffa
2013_02_teneriffa_hiking
2013_02_teneriffa_loro_parque
Another thing are filenames. This is difficult and also depends whether you plan to sell images. IMHO Filenames should always have your initials, the date in the order yymmdd, the original filename and also something short to give a hint which camera was used (if you use more than one camera). Maybe also a hint of what it is dealing about, similar to the second level folder naming.
My problem for example is, that I use besides other cameras also 2 different Sigma cameras. Both Sigma cameras are using the exact same filenames, which is stupid because you risk to overwrite the files by accident. So this is why I am thinking now about software like image ingster, to make sure that immediately, even if I do not want to open Lightroom, the files get a unique naming while they are downloaded to my laptop and from teher to my external HD. Also software like Image Ingster can download at the same time the same file on to two different HD, which saves a lot of time and errors. You the have it on the working HD and on the backup HD at teh same time without doing it all again to copy over.
And these software offers als checking of the files for defects. Also it can at the same time insert already your most important/basic Metadata. So this is really a time saver and security tool.
I do not scan anymore. Since 2004 I do not shoot slides anymore. I will try in the future to scan/photograph the most important slides, so that they are digital and can be backed up easier. ut I will do this probably with a high resolution DSLR and a Macro lens. Scanning just takes too much time and my slides are not worth this
I am curious, what other users are using and how they manage their DAM.
Hope that helps.
Best wishes