Genericide is the term coined to describe the loss of a trademark that no longer serves as an indicator of a source of goods because consumers came to regard the trademark as a generic term. Examples of trademarks lost to genericide include Aspirin, Xerox and Band-Aid.
The July/August  edition of the "ACC Docket" provides some useful tips on how to prevent your trademark from becoming generic:
Always connect the mark to a generic term. The mark should:
be used as an adjective. Not "Xerox", but "Xerox photocopier";
not be used as a noun of any type, singular, plural or possessive. not "put on a band-aid", or "two band-aids", or "band-aid's adhesive quality", but rather "put on a Band-Aid bandage", or "the adhesive qualities of Band-Aid bandages"; and
not be used as a verb (never "Xeroxed", but rather, "photocopied").
Always distinguish the mark from the rest of the text by italics (Ivory soap), capitals (the XEROX photocopier), or some similar method.
On its first use in any materials, the mark should carry, as appropriate, TM, SM, or ®. The ® mark may be used only if registration has actually issued, TM and SM may be used with any mark.
Finally, remember that even your internal use of the mark can be discoverable.
These tips are useful to prevent the loss of your mark to genericide. Keep in mind to also pay your renewal fees and to continue to use your mark. Otherwise, your mark may go abandoned.