Some pointers on using trademark and copyright symbols such as ®, ™, and © effectively:

• It’s okay to use a sans serif symbol with serif text.
• When using a ® or a ™ after a word in text, the symbol should look a little smaller than half the x-height of your text. As the text gets larger, the symbols should appear proportionately smaller.
• When the copyright symbol appears before text, its target size should be the same x-height as the next character that follows it.
• When the copyright symbol appears before a year, its target size should be the height of the smallest number in the group number set.