This is a best practice overview for system administrators, specifically geared toward beginner system administrators while having good information that seniors can refer back to as well. A system administrator is responsible for keeping the software systems of a company running smoothly by being proactive in fixing issues before they cause a crash.
You may be responsible for all of the company's active directory or only a portion of it. Active directory is a very visible part of your job as a system administrator because it controls user access. This means if someone doesn't have the right permissions to do their job or if they can't log in, they're going to be calling you.
These permissions are the first line in a company's security policy so enforcing password policy and group policy is important. Make sure to read or ask a senior administrator what the policy is so you can enforce it when you're setting up new accounts or new groups.
This may vary depending on the size of your company and how the responsibilities are split up, but you may be in charge of ensuring that patches and anti-virus protections are updated. Something to keep in mind with these updates is they can break the very systems you're trying to keep protected.
When possible, run patches through a test before putting them into production so you know what's going to happen and what may need to be fixed before implementing them in a live environment. If that's not possible, roll out the updates slowly so you can see what's happening and test each server and computer before moving onto the next so you're not dealing with a whole bunch of broken computers and servers at once.
You'll also be responsible for upgrading software and operating systems. In these scenarios, test the new software to make sure it does what the end users want it to do and they can still do their jobs. Your goal when doing upgrades is to get the upgrade done as quickly and with as little impact on the end users as possible.
If you're tasked with helping the engineers with migrations, the best thing you can do is look up what's needed for the migration and everything that can go wrong. Especially in physical to virtual machines a lot can go wrong because of licensing, and issues that may be on the physical machine. Looking up all of the documentation you can get your hands on to help prevent problems is the best thing you can do. Also, plan for more time than you think you need because something will go wrong.
Finally, always keep learning. With technology changing, part of your time should be spent reading whitepapers and keeping up on what's going on in your field. Whitepapers and Microsoft's Technet are great resources for learning and staying up to date on new technology.
A system administrator's job is to keep everything running as smoothly as possible while following good policy. A good system administrator isn't noticed, but a great one is noticed because they're improving things all the time.