Never Use Caps
Its a good practice to use all lower case characters in a url.Never try using all caps or first letter caps.Its really confusing.
Kill the spaces
Never use spaces in ur file names.Spaces can lead to the awful %20 signs in your filenames.Avoid using spaces for the same reason.
Use underscores and hyphens
You can use the underscore character and hyphen in place of spaces in your filenames.
Use URL encoding if necessary
Suppose space is unavoidable in the file name, then you must use url encoding for the same so that the space is replaced by a plus(+) sign.
Avoid @#$%&^
Avoid characters like the dollar sign and ampersand symbol.
Use short to-the-point filenames
Use filenames that are precise, yet simple.
Organize your content based on filetype
Split your site into many folders like images, scripts, media,files and pages.
Organize your content based on use
Split your content based on use and requirement.
Protect premium content / Restrict access
Restrict access to certain [...]

Original story: Noor Cholish