Every time I need to find one of these I always end up searching for the key combinations to write the special characters and in an effort to save time for you (and myself), I’m going to include the most common ones here.

For Microsoft Windows:

Note: Use all this codes with the combination of Alt. For Example you need to type © than press and hold the “Alt” key and type 0169.

© - 0169
® - 0174
™ - 0153
• - 0149
§ - 0167
† - 0134
‡ - 0135
– - 0150
— - 0151
¶ - 0182
¥ - 0165
§ - 0167
¼ - 0188
½ - 0189
¾ - 0190
À - 0192
Á - 0193
» - 175
÷ - 246
ø - 0248
þ - 0254
ß - 225

For Mac OS X:

These are a lot easier to figure out on your own. You basically just use the option key as a modifier with any other key and see what happens. Here is a chart of the most popular ones:

© - Option+G
® - Option+R
™ - Option+2
¶ - Option+7
• - Option+8
§ - Option+6
– - Option, then minus sign i.e. Option+-
— - Shift+Option+-
† - Option+T

For a more complete list of the character palette for the Mac check out this page, for accents, check out this page.