Part One and Part Two.
To this point you should have an understanding of how to get your images organized in such a way that makes finding them easier. Although the previous method discussed was about organizing personal images the same holds true for client work, with some minor adjustments.
If you are a working professional, many of your private images likely cross over to your paid work. Technically you can claim that you are your own client but let's not confuse things.
There are two basic systems you can utilize to keep track of client work, depending on the type of client and their requirements. The first is a typical client with one of a kind project.
From here the structure resembles the Personal structure but without the year folder. A year folder is only suggested if the client does large volume work and not having that segregation would make the directory too long. Otherwise the naming convention is the same as the Personal one, year-month-day followed by the project name (or number) given by the client or a brief description of the job.
Just as previously, you separate the keepers from the seconds and the edits from everything else.
The second variation is for clients who have a complex project system. For example, a catalog project where there are multiple products shot over the span of a couple of months. The project name would be the same but there would be several shooting events.
Another example would be a design firm who hires you to work on several projects for their own clients. The design firm would be your client but their clients would be the firm's projects. Everything else gets sorted out like before, keepers, seconds, edits, etc.