<p>I have Excel add-in which I add so many class modules that it is now very bulky. I want to convert it into a type library or a COM package so that I can re-use it for the other apps in the MS Office suite.</p>

<p>I ported the add-in to Visual Studio as a class library project but Excel Automation doesn't recognize the classes in the compiled .dll file. Intuitively I think I would need a manifest, an interface or the something like that in my code.</p>

<p>What do I need to know in order to expose a class's methods and properties for use in OLE Automation?</p>

Here's a list of
general naming conventions
from MSDN.
I tend to just go-with-the-flow, however.  Whatever standards are currently in place, it's usually easiest to just go with them and maybe slowly shift it over time. It's not really practical to just come into a project with your own idea of "standards" and try to implement them.
It doesn't REALLY matter what standards are used, imo -- just that there are some and people know what they are.