Wikipedia’s definition: A password is a secret word or string of characters that is used for authentication, to prove identity or gain access to a resource (example: an access code is a type of password). The password must be kept secret from those not allowed access.
Scanning through the early pages of the Unix Visual Quickstart Guide 2nd Ed. by Deborah and Eric Ray, it says choose a password that is:
1. At least 6 characters long (I consider 10 as minimum).
2. Easy for you to remember.
3. Not a word or name in any dictionary in any language.
4. Any combination of capital and lower-case letters, numbers, and symbols.
5. Not similar to your username.
6. Not identical or similar to one you’ve used recently.
7. Not your telephone number, birth date, kid’s birth date, anniversary, mother’s maiden name, or anything else that anyone might associate with you (uhmm… pet’s name Bill?).
Cheers!
Update: By the way, there is already the Unix and Linux: Visual QuickStart Guide (4th Edition – Paperback – July 8, 2009).
Scanning through the early pages of the Unix Visual Quickstart Guide 2nd Ed. by Deborah and Eric Ray, it says choose a password that is:
1. At least 6 characters long (I consider 10 as minimum).
2. Easy for you to remember.
3. Not a word or name in any dictionary in any language.
4. Any combination of capital and lower-case letters, numbers, and symbols.
5. Not similar to your username.
6. Not identical or similar to one you’ve used recently.
7. Not your telephone number, birth date, kid’s birth date, anniversary, mother’s maiden name, or anything else that anyone might associate with you (uhmm… pet’s name Bill?).
Cheers!
Update: By the way, there is already the Unix and Linux: Visual QuickStart Guide (4th Edition – Paperback – July 8, 2009).
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Update: Feb 8 2010, 11:16 PM
Just to add, this page can help... Strong Password Generator (w/ crazy mnemonics) 
http://strongpasswordgenerator.com/
http://strongpasswordgenerator.com/
