The simplest explanation for how to trademark an idea is that you cannot do so. Trademarks provide protection for names, logos, and other types of identifiers that indicate which business has made a product or provided a service for customers and clients. This type of protection is extended to actual things that can be seen or read, which are used to identify one business from another and avoid customer confusion while providing protection of intellectual property. Since an idea is not typically considered a real form of intellectual property, you cannot trademark an idea.
Even though you cannot trademark an idea, there are three major ways in which you can protect a given form of intellectual property. All of these methods protect something that is real or at least visible, something that has gone from being an idea to being a reality. Copyrights protect works of art and artistic creations, including everything from drawings and poems to pieces of music and architectural designs. Patents are used to protect inventions and machines, those that establish new ways of doing things or new versions of an established concept. A trademark is established to protect intellectual property that serves to identify a product or service provided by a business, and you cannot trademark an idea because it does not serve as such an identifier.
Intellectual property protection extended through these types of marks protect only an actual product or realized creation. You cannot trademark an idea simply because as a concept, ideas do not constitute actual property. This would be similar to someone attempting to declare ownership of a hypothetical landmass that may arise at a future date due to volcanic activity beneath the Earth’s oceans. You cannot trademark an idea because you cannot trademark the potential or concept of something, only an actual thing that serves to identify your business or services.
When you register a trademark, you must also provide a drawing of your trademark and you will usually need to provide a sample of the trademark in use. Since an idea exists in an ephemeral sort of way, you could not provide a drawing of an idea, and so you could not trademark it. Being able to trademark an idea would also create great potential for abuse, as various businesses and individuals could lay claim to entire concepts, thereby eliminating any risk of competition since the very idea of a particular product or service would be protected by trademark.