You can follow guidelines to create a secure password.
It is not necessary to incorporate all of the following rules in one password the more rules you use, the better your chances are of making your password more secure:
Passwords should be 6-14 characters long. (Mac passwords cannot be longer than 8 characters)
Avoid using the “illegal” characters: *, ", or spaces
Avoid using words from dictionary (in any language)
Do not make common letter substitutions, like replacing E with 3, or L with 1
Include characters from as many of these classes as possible:
Uppercase letters
Lowercase letters
Numbers
Symbols