Trademark symbol

TM symbol
The symbol TM is used to provide notice of a claim of rights in a trademark. A TM is usually used in connection with an unregistered trademark and is used to inform potential infringers that a term, slogan, logo, or other indicator is being claimed as a trademark. Use of the symbol TM does not guarantee that the owner's mark will be protected under trademark laws.

SM symbol
The symbol SM functions similarly to the TM symbol, but is used in connection with services, such as banking services or legal services, rather than tangible goods. Use of the symbol SM does not guarantee that the owner's mark will be protected under trademark laws.

® symbol
The ® symbol is a notice used in many countries or regions to advise the public that a trademark or service mark is registered and providing constructive notice of the legal ownership status of the mark with which it is used. The ® symbol should be used only in connection with registered marks. Use of ® with any unregistered trademark may result in claims of fraud or other difficulties in trying to obtain and/or enforce trademark rights.

Proper use of a trademark symbol
There is some flexibility on how and where to use the TM, SM and ® symbols. Placing it at the upper right hand corner, the lower right hand corner, or level with the mark or logo itself are all typically acceptable ways of displaying the appropriate symbol. These symbols are most often placed adjacent to the mark in superscript (smaller, raised) form.

Source

 * INTA, "Fact Sheets: Introduction to Trademarks" (full-text).