What's the correct way to name files and folders?

I'm restructuring my static site and I'm reading mixed opinions about how to name and structure files and folders and I'd like to get this squared away properly.

If I have several topics about bankruptcy like "filing bankruptcy", "bankruptcy services", and "get bankruptcy protection", can all of these be under the same folder named bankruptcy? or can I create a folder for each sub category. As in filing_bankruptcy, bankruptcy_services etc. I know that each sub folder should have an index.html page, but what about additional articles that I write, what's the proper way to name those files if they happen to be targeting long tail keywords, like "don't file bankruptcy alone" or "bankruptcy services in your area". If I was going to write articles for these keywords, it seems like I should be naming these files by the name of the long tail, separating each word with an _ or a -.

This is where I'm not having much luck, I can't seem to get this right. My main concern here is the use of long tail keywords for article names and directory names. I know it's not a good idea to make the URL longer than it needs to be, and maybe I'm trying to hard to be granular focusing on keywords.

Any help on this I'd appreciate it, Thanks.

Charlie.