Create and use strong passwords, and change them often enough that it's unlikely that a cracker would have managed to guess them. Make any users on your machine do the same. Run the same tools that the crackers are going to use against your passwords yourself, and find out where your weaknesses are. Always assume that the people who want into your machine have got more CPU to throw at the problem than you do, and always assume that they've already got a copy of your password file and that the clock is ticking. You aren't doing anyone any favors by allowing users to use weak passwords because they're computer novices and strong passwords will be too difficult for them to remember. When their accounts are broken into and trashed because they used poor passwords, it'll bother them a lot more than having to remember strong passwords.
On the other hand, don't trust that anyone has your best interests in mind while you're working to protect their best interests. The legal system has only the faintest clue how to apply the existing laws to computer issues, and the legislative branch of the U.S. government is going out of its way to pander to the deep-pocket special interests to write yet more bad laws regarding computer security. Make absolutely certain that you know what you're expected and allowed to do on the systems you're securing, and get it in writing. It might save you a fair chunk of change in legal fees someday.
Oh, and although I shouldn't have to mention it, people who write down their passwords on post-it notes and stick them to their monitors , inside their pencil holders, or in their desk drawers, should have their computer (as well as several more life-critical) privileges revoked . People who think they're clever and stick them to the bottoms of their desk drawers aren't much better. Don't write down, share, or otherwise let your passwords out of your skull. Mandate enforceable sanctions against users who do any of these things, and then enforce them.
Password security isn't fun, and as long as we've got to live with the simplicity of the small key space and ever increasing CPU power, it's going to get less fun as time goes on, but it's something we've got to do. People who refuse to take the issue seriously are endangering their, your, and every other person on the system's data and security, and are acting in a manner completely disrespectful to your and other user 's very reasonable security concerns. If they've not the slightest shred of consideration for you, you've no obligation to show the slightest consideration to them, as you boot their sorry behinds off the system.