Mac 101: Inserting or typing uncommon characters

As a Mac consultant, I’m often asked some pretty bizarre questions. One that I frequently hear is “How do I type <some special character> on my Mac?” A good example of this is people who want to type fractions that look like this — ½ — rather than like 1/2, or plop a character like an umbrella — ☂ — or a skull and crossbones — ☠ — in the middle of a sentence — via TUAW