Browsing this forum and the internet in general, I found little information on the subject of copyright/trademark symbols--mostly details about which one should legally be applied where, but nothing on their design.
©,®, and ™ seem to vary greatly from font to font. Sometimes they are as big (or bigger than) the caps, sometimes they're superscripted.
Sometimes the ring surrounding the Registered and Copyright marks is hairline, sometimes the same thickness as the letters.
On my display fonts, I like to give them some personality, for instance by turning the "TM" into a ligature, and by matching the surrounding ring to the rest of the typeface. I also tend to adjust letterforms (especially the R) to fit better inside of their circle. I feel comfortable doing so because I doubt any of these fonts will make their way into legal documents anyway, so I might as well have some fun with it. If they ever get used for a big-time logo, the designer can just add the ® from Helvetica or whatever.
What do you consider best practice and why? Also, feel free to show off your favorite marks!