Your password can include almost any character you can type (the main exceptions being control keys and the Return key). A good password is one that you can remember readily, but which no one else can easily guess. Examples of bad passwords include:
Words that can be found in a dictionary
Any common or popular name
The name of a famous person or character
Your name or username in any form (for example: backward, repeated twice, and so forth.)
A spouse's, child's, or pet's name
Your birth date or a relative's birth date
Social Security number, driver's license number, passport number, or similar identifying number
Any sample password that appears in this or any other manual
A good password is at least eight characters long. Moreover, a password should include a mix of characters, such as upper- and lower-case letters, numbers, and punctuation marks. Examples of passwords that would be good if they didn't appear in this manual include:
Acronyms, such as "I2LMHinSF" (recalled as "I too left my heart in San Francisco")
Easy-to-pronounce nonsense words, like "WumpaBun" or "WangDangdoodle!"
Deliberately misspelled phrases, such as "6o'cluck" or "RrriotGrrrlsRrrule!"
 Caution -
Caution - Don't use these examples. Passwords that appear in manuals are the first ones an intruder will try.