The systems staff will never need to know your password for any legitimate purpose. Anyone claiming to be systems staff who requires your password is trying to deceive you. DO choose a password that has no easily discerned signifigance to you. DO choose a password that is six to eight characters long. DO memorize your password.
Passwords are case-sensitive.
DO choose a completely new password every time you change. Once they get your password, they can do awful things to any information stored in your account. Even worse, they may be able to do awful things to the accounts of other people on the system, or even break in to systems across the world from ours. System security is everyone's responsibility. Because you don't know where the information will go after it leaves your lips.