NARA Blog – “The following are best practices for file naming. File names should:

• Be unique and consistently structured;
• Be persistent and not tied to anything that changes over time or location;
• Limit the character length to no more than 25-35 characters;
• Use leading 0s to facilitate sorting in numerical order if following a numeric scheme “001, 002, …010, 011 … 100, 101, etc.” instead of “1, 2, …10, 11 … 100, 101, etc.”;
• Contain a file format extension;
• Use a period followed by a file extension (for example, .tif, .jpg, .gif, .pdf, .wav, .mpg);
• Use lowercase letters.  However, when a name has more than one word, start each word with an uppercase letter for example, “File_Name_Convention_001.doc”;
• Use numbers and/or letters but not characters such as symbols or spaces that could cause complications across operating platforms;
• Use hyphens or underscores instead of spaces;
• Use international standard date notation (YYYY_MM_DD or YYYYMMDD);
• Avoid blank spaces anywhere within the character string; and
• Not use an overly complex or lengthy naming scheme that is susceptible to human error during manual input, such as “filenameconventionjoesfinalversioneditedfinal.doc”.”