How do I prove that my mark has secondary meaning?
If your mark is descriptive, it is not inherently distinctive and you must show that the mark has acquired secondary meaning (distinction among the consuming public) in order to fully protect the mark (although a descriptive mark without secondary meaning can be federally registered on the Supplemental Register, this affords you little protection). There are many things that can be used in showing that your mark has acquired the necessary secondary meaning. The most common evidence, and arguably the strongest evidence, is through consumer surveys. If you conduct surveys of the relevant buying public and these surveys show that many consumers associate the mark with you (rather than associating it with the class of products as a whole), this is strong evidence that your mark has acquired source indicating properties in the minds of the public. In addition, the more sales and advertising you have done, and the length of time you have used the mark, can weigh in favor of your mark having secondary meaning.
While you can gather this evidence on your own, it is recommended to seek the help of a trademark attorney familiar with trademark protection and litigation, who can help you interpret and present the evidence in a compelling fashion.