If one is filing a file by the company name of Don Hummer Trucking, which is a business, would on e file the under "D" or "H?" Thank you

Since the Business name is "Don Hummer Trucking" it would be filed under D.

The instances where you would break this rule is if it were "The Don Hummer Trucking Company" or "A Trucking Company" where you would bypass the first word of the company name and file it under the D or T

You could file under "D" for Don as the entire name of the business is Don Hummer Trucking. You would not use "H" as this is not the first name of the company.