Spanish Accents and Characters using a Macintosh Computer

To get accents on the Mac, hold down the Option key, and while holding it down, type the letter e; then release those keys and type the letter that you want the accent to appear on:

á = Opt + e, then a
é = Opt + e, then e
í = Opt + e, then i
ó = Opt + e, then o
ú = Opt + e, then u

For the ñ, hold down the Option key while you type the n; release and type n again.

ñ = Opt + n, then n

To place the diaeresis over the u, hold down the Option key while pressing the u key; release and type u again.

ü = Opt + u, then u

The inverted punctuation marks are achieved as follows:

¡ = Opt + 1
¿ Opt + shift + ?

(Instructions from http://www.studyspanish.com/accents/typing.htm)