Instructions for generating Spanish characters in Microsoft Word for Windows
Letters with accents: CTRL + ' (APOSTROPHE), then the letter you want accented
ñ or Ñ : CTRL+ SHIFT + ~ (TILDE), n or N
¿ : ALT + CTRL + SHIFT + ?
¡ : ALT + CTRL + SHIFT + !
For programs other than Microsoft Word, you will need the list of extended ASCII characters. You simply press ALT and the number of the character that you want IN THE KEYPAD in your keyboard. For instance, to produce "ó" you would press ALT + 162; to generate "ñ" you press ALT + 164. Make sure the keypad is active by pressing the NumLock toggle key. Do not use the number keys in the top row of your main keyboard. For an abbreviated list of ASCII characters that you will use frequently, click here.
A lot of people prefer this method (even if it takes your fingers away from the main keyboard) because it is easy to memorize the code for each character and it can be used within Word as well as with all other programs.
Alternatively, you could follow the instructions to change your keyboard layout to Spanish, and generate the characters you want directly from the keyboard in any program.