Depending on the language you are looking to use to create the COM object there are a few good txts available on the the subject.
"Inside COM" - Dale Rogerson and "Essential COM" - Don Box; are both very good books with great coverage and explaination of the common object model. Also "ATL Internals" - by Brent Rector covers COM creation using Microsoft(r) Active Template Library (ATL).
You might want to look in to these books, they are old enough they should be available at a good library. Also if using the newer dotnet framework, you can get some examples of using C# to create COM objects at CSharp Help