This is a question I get a lot from clients who are thinking of – or even starting to – register their logos as trademarks.
Here's some advice from the US Patent and Trademark Office website:
Anyone who claims rights in a mark may use the TM (trademark) or SM (service mark) designation with the mark to alert the public to the claim. It is not necessary to have a registration, or even a pending application, to use these designations. The claim may or may not be valid.
The registration symbol, ®, may only be used when the mark is registered in the PTO (Patent and Trademark Office). It is improper to use the registration symbol at any point before the registration issues.
Please omit all symbols from the mark in the drawing you submit with your application; the symbols are not considered part of the mark.
It's actually a bit of a tricky issue. There's the TM symbol, which basically means "I'm thinking about, or am in the process of registering my design as a trademark – or I just have this design and want to claim it as protected".
Then there's also the ® (register mark) symbol, which means "I went through the paperwork with the US Patent and Trademark Office and registered this thing!". You're not allowed to use this symbol in trade until you get the certification that your logo has passed their tests.
So, you should actually go through a 2-step process, technically. And wind up with 3 sets of logos: No symbol (you need this to register, and it can come in handy down the line, in case you're printing anything that's too small to have the TM symbol look good), TM and register-marked.
But, what does that mean to your materials?
It means that you'd have to create 2 more sets of logo files (they take about 30 minutes each to generate, and aren't included in the standard package deliverables). But, that's the easy part.
It also means preparing and printing business cards twice, or waiting to print them. Once with the TM and then again with the ®.
And, that extends beyond just business cards – you'd have to change it everywhere. On anything you have printed as well as all digital instances of your logo – your Microsoft Word letterhead, invoice header, website, Facebook Fan page…
What do you do?
I've had companies go through all of the iterations (because, who knows how long it will take the USPTO to process your stuff).
I've had companies just wait and go to the ® (skipping the TM version) when they're registered.
I've also had companies who are registered decide not to add the symbol, ever, even though they're registered. They tend to put notices in their legal materials on their website.
I'm not a trademark lawyer, so I can't tell you which is best. If you're really concerned about this issue, you might want to find a lawyer and talk to them about it.