NOTE: there are other tagging programs out there, like Adobe Bridge and ACDsee. I'm not familiar with these other programs (I do use Bridge but not for organizing my stash) but I'm sure something similar an be done.
NOTE 2: If you're using LR, it is important that you get LR5 if you use my method, which moves the files around. LR5 will import PNG files, the previous versions won't!
This is how I organize my stash in Lightroom (be warned, this is gonna be long)...
1. First, upzip your downloads. I do this right in my Downloads folder, and when I unzip I select no path names to get rid of the folder structure in the zip file. It just makes it faster for me to see everything in the unzipped folder. IMPORTANT: sometimes designers name their files the same names in different folders. For example, if a kit has 2 alphas, a red and a blue one, and they're placed in separate folders but named the same (designer_kit_A for instance), when you unzip the red alpha will overlap the blue one when being brought into the same folder. It's important to check after you've unzipped if you have files missing.
2. After unzipping the files, I go into each folder and delete the shop links, TOU, and other unnecessary files. I keep a copy of the designer's TOU in their main folder but I don't need a hundred copies of it. Then, I rename the preview "00Preview." This keeps it as the first file in the folder.
3. After I go through all the unzipped folders in the Downloads folder, I move them into a Sorting folder. This is what it looks like. It's split into a number of different folders in alphabetical order.
4. Putting the folders side by side, I move the unzipped folders from Downloads to Sorting. Here, I'm moving a folder into my Kristin Aagard folder, located in "K to L."
5. For kits, I put the papers and elements into one folder, and have one preview for the kit. I do like to keep journal cards and alphas (and sometimes word art packs) separate with their individual previews, because these are things I can easily mix-and-match.
6. When everything's sorted into their right designer folder in the sorting folder, it's time to import them into the Lightroom catalog. Open up LR, start a new catalog if it's your first time, and click "Import"or ctrl+shift+I. This will bring up the following window. On the left hand side is "source," or where your files are to be imported (in my case, it's the sorting folder), and on the right is "destination," where you want your files to go. On the top, note the different options of how you want your files to be handled. You can "add," which means the files will stay where they are but their previews will be imported into LR for you to tag. You can "copy," which means the files will stay where they are, and a copy will be made in the destination. In my case, I want my files to go into my EHD so I always choose "move," which moves your files from the source to the destination. Finally, under the word Destination, you choose how you want your files organized. Uncheck "into subfolders," and leave it as "organize by original folders."
7. Next, choose the folder you want to import on the left hand side (the source). My sorting folder structure is EXACTLY the same as the one on my EHD. This is very important as LR will merge the folders you're trying to move if their names are the same, thus helping you add new kits you've bought into the same designer folder. For example, from my sorting folder, I have a Bella Gypsy folder in the "# to B" folder. On my EHD, there is also a Belly Gypsy folder in a "# to B" folder. Because the names are the same (do make sure they're exactly the same), I can import the two new kits I got from BG into the existing BG folder.
When importing, choose the folder you want to import on the left hand side (the Bella Gypsy folder) and the folder one level higher on the right hand side (the # to B folder). This will ensure the folder you want to import goes right where you want it to be.
8. You don't have to do it by designer. I usually do it by a chunk of alphabets (the # to B, then the C to D, then the E to J folder). Once you make sure that the folder structure is right and your folders are merging correctly on the right hand side, click Import. LR will start importing and you can see its progress in the bar on the upper left corner. This may take a while depending on how many images you have and how you're importing them.
9. After LR is done importing, click on "Previous Import," which will show you all the images you've just imported. Move down to the bar where it says "Sort:" and choose File Name. Because all your previews have been named "00Preview," this should bring them to the very top and allow you to tag them with ease. To tag your previews, look to the right hand side, and click "keyword list." Here you can create a list of tags (and you can create tags within tags). Simply click on the tag and a check will appear, meaning your image has been tagged. I tag my previews by shop (but not designer as my folders are already structured by designer), license, colors and themes, and also what they are (kit, alpha, journal card, etc).
10. For template packs, I break them up and put templates in folders depending on their number of photo spots.
11. When importing, I simply import the entire folder into the existing one. If necessary, I will tag the templates further (pocket templates, hybrid templates, complete albums, and so on).
12. Note that once your catalog is set up, it's important to move the folders within LR. You can do this by dragging the folders to other locations. If you move your files outside of LR (say in Windows Explorer), LR will think the files are missing...
14. And show you the dreaded exclamation marks and question marks. You can redirect LR to the new file locations but it's just a pain to do so. So when I need to move my folders (and I try not to do it at all, which is why it's important to have your folder structure in the exact place you want it from the beginning) I do so within LR.
15. To utilize the system, go to the top to the Library filters, and select "keyword." This will bring up the keyword list and you can click on a tag to bring up things tagged with it. You can combine tags to refine your search. For example, here I have "Scrap Orchard" and "Birthday" selected, and 1 kit comes up that's been tagged with both. To access it, right click on the preview and click "Show in Explorer." This should bring up your kit!!
I hope that's been useful! It's a little confusing when you first start but once you have done it two or three times you wouldn't even be thinking about it. :) Let me know if you have any questions!