Go to System Preferences>International. Click the Input Menu tab and turn Character Palette on by checking its box. Then, click Show Input Menu In Menu Bar (bottom of the International window).
You'll get an American flag icon at the right side of the menu bar. Click it to show Character Palette. Be sure that By Category is selected and then select Accented Latin from the list. You can drag the appropriately accented letter into your document (or this post). I am doing it now with á and voilá. You can also click Insert to put it at the insertion point.
The keyboard shortcut is to press Option E and then A. I know this from an app that I acquired back in Jaguar called Font Explorer. The company has now renamed it
Font Examiner if you are at all interested in it.
EDIT: I put the wrong accent on the a in voilà .
If you want to know, the key combo is Option ` and then A.