For my architectural photography business, I separate all projects in folders first by client and then by project name/address. With in each project folder, I have all RAW files for each image captured in their own folders with all raw adjustments. Each project folder contains a folder title "Edited" in which all of the working files are stored followed by "Finished" with the flattened Photoshop files. "Client" folder is also within the project folder with the deliverable files, usually full res JPEGs and web-sized JPEG.
Now for this business, only I would ever go into my database. However, for my backdrop business I have partners that may need to find an image in our fairly extensive stock catalog if say I am on vacation.
So, here all images are broken into six overall genres (with six corresponding folders), Urban, Suburban, Rural, Landscape, Coastal and Clip Art. Next, the images get broken down by state or country, then by city/town, then by neighborhood (for large cities). For an image titled U-NY-NYC-ES14-25 would be found by going to the folder Urban, then New York, then New York City, then East Side. The 25 at the end is a quick reference for us to know when the image was captured. These are always the working master files anywhere from 2 GB to 95 GB (our largest backdrop file), and the RAWs are stored in the end folder as well.