You may or may not have the Input menu activated in your menu bar (it’s the one with the flag icon, the flag representing the language of your current input setting); you may or may not have the Character Palette listed in the menu. But you can open the Character Palette from an application’s Edit menu, or with a keyboard command whether you have the Character Palette in the Input menu or even if you don’t have an Input menu at all.
Programs that strictly follow Apple’s interface guidelines (that’s most Apple programs, including the Finder) provide a Special Characters command in the Edit menu, which opens the Character Palette. Programs that don’t follow the guidelines include those from Microsoft (surprise!) and Adobe (surprise again!).
The keyboard shortcut to trigger the command is Command-Option-T.
Why would you ever need the Character Palette? Well, check out the tip on making Excel in-cell graphs look like bars.
For programs that don’t provide this command, see the tip on how to add the Character Palette to the Input menu.