A federally registered trademark is a valuable asset for your business and should be properly cared for. If a trademark is misused by its owners (or others), it can be lost. Therefore, you must constantly police how and where your trademarks are being used. Luckily, the world's preeminent organization for trademark owners and professionals, the International Trademark Association (known as "INTA" to friends) is here to help. INTA has provided a quick and easy way to educate yourself and others on the right way to use your trademark. INTA calls it the ACID test, which stands for:
Adjective: Always use the mark as an adjective, not a noun ("I would like a KLEENEX tissue" not "Hand me a KLEENEX" )
Consistent: The mark should be used the same way each time (If you use all capitals, always use all capitals)
Identification: Always indicate that the word is being used as a trademark by using the ® symbol for federally registered trademarks and ™ for unregistered marks
Distinctive: Always display the trademark in a way that separates it from the surrounding text (bold, italics, all caps, or by using one of the foregoing identifiers)
Further explanation can be found in INTA's A Guide to Proper Trademark Use for Media, Internet and Publishing Professionals.
INTA's ACID test is a convenient way to remember how to properly use your trademarks. In fact, if you apply the ACID test, your trademarks will be happy to be "used" (it is believed in trademark circles that Bill Withers' famous song "Use Me" is the first and only popular song told from the perspective of a properly used trademark).