Write a short phrase describing what the 30th anniversary plaque is for. For example, if you are commemorating an employee's 30th anniversary with a company, you could write something like "For 30 Years of Service." If the plaque is for a wedding anniversary you could write something like "For 30 Years of Magic" or "For 30 Years of Love."
Write the name or names of the people involved with the anniversary. For a work-related anniversary, you could include the name of the employee and the name of the company. For a wedding related anniversary, you could include the name of the husband and wife, or "Mr. and Mrs. [Last Name]."
Include the anniversary date on the plaque. You can include the actual date of the anniversary in "Day, Month, Year" format or just the year of the anniversary depending on your preferences.