My 2 ¢ on the trademark symbol and other similar stuff:

For accented letters and characters like ©®™ I use the compose key. It's quite handy and the mnemonics are easy to remember:

© [Compose] + o + c
™ [Compose] + t + m
ô [Compose] + o + ^

You can enable it via the TDE keyboard settings and set it to the key you want (Right Alt suits me just fine).

--
Philippe