When you come into a new job, or start working with a new technology, you may have all sorts of bright ideas. If you're new to the workplace, you immediately hone in on those things that your predecessors were (or seem to have been) doing wrong. You're full of all the best practices and tips and tricks that you learned in school. If you're an experienced administrator coming from a different environment, you may be set in your ways and want to do things the way you did them before, rather than taking advantage of features of the new OS. Either way, you're likely to cause yourself a great deal of grief. The best bet for someone new to Windows networking (or to any other job, for that matter) is give yourself time to adapt, observe and learn, and proceed slowly. You'll make your own job easier in the long run and make more friends (or at least fewer enemies) that way.
#2: Overestimating the technical expertise of end users
Many new administrators expect users to have a better understanding of the technology than they do. Don't assume that end users realize the importance of security, or that they will be able to accurately describe the errors they're getting, or that they know what you mean when you tell them to perform a simple (to you) task such as going to Device Manager and checking the status of the sound card. Many people in the business world use computers every day but know very little about them beyond how to operate a few specific applications. If you get frustrated with them, or make them feel stupid, most of them will try to avoid calling you when there's a problem. Instead they'll ignore it (if they can) or worse, try to fix it themselves. That means the problem may be far worse when you finally do become aware of it.
#3: Underestimating the technical expertise of end users
Although the above applies to many of your users, most companies will have at least a few who are advanced computer hobbyists and know a lot about technology. They're the ones who will come up with inventive workarounds to circumvent the restrictions you put in place if those restrictions inconvenience them. Most of these users aren't malicious; they just resent having someone else in control of their computer use - especially if you treat them as if they don't know anything. The best tactic with these users is to show them that you respect their skills, seek out their input, and let them know the reasons for the rules and restrictions. Point out that even a topnotch racecar driver who has demonstrated the ability to safely handle a vehicle at high speed must abide by the speed limits on the public roads, and it's not because you doubt his/her technology skills that you must insist on everyone following the rules.
#4: Not turning on auditing
Windows Server operating systems have built-in security auditing, but it's not enabled by default. It's also not one of the best documented features, so some administrators fail to take advantage of it. And that's a shame, because with the auditing features, you can keep track of logon attempts, access to files and other objects, and directory service access.
Active Directory Domain Services (AD DS) auditing has been enhanced in Windows Server 2008 and can be done more granularly now. Without either the built-in auditing or third-party auditing software running, it can be almost impossible to pinpoint and analyze what happened in a security breach.
#5: Not keeping systems updated
This one ought to be a no- brainer: Keeping your servers and client machines patched with the latest security updates can go a long way toward preventing downtime, data loss, and other consequences of malware and attacks. Yet many administrators fall behind, and their networks are running systems that aren't properly patched. This happens for several reasons. Understaffed and overworked IT departments just may not get around to applying patches as soon as they're released. After all, it's not always a matter of "just doing it" - everyone knows that some updates can break things, bringing your whole network to a stop. Thus it's prudent to check out new patches in a testbed environment that simulates the applications and configurations of your production network. However, that takes time - time you may not have. Automating the processes as much as possible can help you keep those updates flowing. Have your test network ready each month, for instance, before Microsoft releases its regular patches. Use Windows Server Update Services (WSUS) or other tools to simplify and automate the process once you've decided that a patch is safe to apply. And don't forget that applications - not just the operating system - need to be kept updated, too.
#6: Getting sloppy about security
Many administrators enforce best security practices for their users but get sloppy when it comes to their own workstations. For example, IT pros who would never allow users to run XP every day logged on with administrative accounts think nothing about running as administrators themselves while doing routine work that doesn't require that level of privileges.