Hi,
The AP Style Guide says that a trademark is a symbol, brand, word, etc that is used by a manufacturer/dealer to prevent a competitor frm using it. It is protected by law for this purpose. The AP Style Guide says to use the generic equivalent when possible unless the trademark is essential.
For example, the term "Realtor" is trademarked by the National Association of Realtors. Following AP guidelines, use "real estate agent" (or a comparable generic term) instead unless you have a compelling reason to use the word Realtor. If you must use the word "Realtor," you must capitalize it as I'm doing here.
It's my understanding that this is acceptable use without any symbols. For example, I believe this is fine:
I hired a real estate agent to help me sell my home. I wish I would have hired a professional Realtor who worked locally.
Whereas, the next example is not necessary:
I wish I would have hired a professional Realtor® who worked locally.
If you were a competitor rather than a general writer, then trademark symbols might play a bigger role. Like if you just developed a new operating system that competed directly with Microsoft Windows, you might not be able to say something like this:
"Minirock's Clear View operating system compares to Microsoft Windows Vista"
without the trademark symbol. Instead, you probably would have to say:
"Minirock's Clear View operating system compares to Microsoft® Windows Vista" (and I have no clue where the ® symbol should go - after MS or Vista or Windows or all three).
To make it more confusing, what if you are simply writing a review of the new operating system? In this case, you're not the competitor, you're just stating your opinion. I'm guessing that you don't need to include the trademark but I don't know for sure.
The AP Guide lists this site as a resource:
www.inta.org/index.php
I haven't checked it out yet but it may help you out.
Hope that helps! Can you imagine all the symbols if we had to include symbols and trademarks in general writing? I'd have to go back and edit my earlier post about Coors Light to either say Coors Light® or light beer.