Do Not Use Only Words or Numbers — Never use only numbers or words in a password.

Some insecure examples include the following:

Do Not Use Recognizable Words — Words such as proper names, dictionary words, or even terms from television shows or novels should be avoided, even if they are bookended with numbers.

Some insecure examples include the following:

Do Not Use Words in Foreign Languages — Password cracking programs often check against word lists that encompass dictionaries of many languages. Relying on foreign languages for secure passwords is not secure.

Some insecure examples include the following:

Do Not Use Hacker Terminology — If you think you are elite because you use hacker terminology — also called l337 (LEET) speak — in your password, think again. Many word lists include LEET speak.

Some insecure examples include the following:

Do Not Use Personal Information — Avoid using any personal information in your passwords. If the attacker knows your identity, the task of deducing your password becomes easier. The following is a list of the types of information to avoid when creating a password:

Some insecure examples include the following:

Do Not Invert Recognizable Words — Good password checkers always reverse common words, so inverting a bad password does not make it any more secure.

Some insecure examples include the following:

Do Not Write Down Your Password — Never store a password on paper. It is much safer to memorize it.

Do Not Use the Same Password For All Machines — It is important to make separate passwords for each machine. This way if one system is compromised, all of your machines are not immediately at risk.

Make the Password at Least Eight Characters Long — The longer the password, the better. If using MD5 passwords, it should be 15 characters or longer. With DES passwords, use the maximum length (eight characters).

Mix Upper and Lower Case Letters — Red Hat Enterprise Linux is case sensitive, so mix cases to enhance the strength of the password.

Mix Letters and Numbers — Adding numbers to passwords, especially when added to the middle (not just at the beginning or the end), can enhance password strength.

Include Non-Alphanumeric Characters — Special characters such as &, $, and > can greatly improve the strength of a password (this is not possible if using DES passwords).

Pick a Password You Can Remember — The best password in the world does little good if you cannot remember it; use acronyms or other mnemonic devices to aid in memorizing passwords.