The two most common ways of protecting your logo are with the ™ symbol and the ® symbol. The ™ symbol may be used when trademark rights are claimed in relation to a logo, but the logo has not been registered with the government’s trademarks office, while the ® is used to indicate that the logo has been registered. It is not mandatory to use either symbol. However, in some jurisdictions it is unlawful to use the ® symbol in association with a logo when it is not registered with the government.
Talk to an intellectual property attorney about protecting your logo through a trademark. Such an attorney can also help you make sure your logo doesn’t unknowingly infringe on another’s trademarks, which could produce a situation where you had to change your logo after it is already establish.