New Casper Admin: What piece of advice you would give to a new system administrator?

If you can't already learn to script! Once you are familiar with scripting there is not much you can't make a mac do with Casper.

Yeah, I'd second @Look's advice on learning scripting, assuming you don't already know how to. The thing about the Casper Suite is, although it does a ton out of the box, some of the real power of the suite comes when you can write scripts to do everything from capturing additional inventory information (Extension Attributes) to custom messaging (Applescript, cocoaDialog, jamfHelper, etc) to custom installation procedures, and even scripts you can build into packages within Composer (preinstall, postinstall). It almost becomes crucial to know how to do some scripting, or at least be able to read them well enough to modify existing ones posted here on the community and elsewhere.

And speaking of Composer, I'm not sure how much packaging you've done, but if its a new area for you, take the time to read through some of the threads here about packaging techniques. Many new people to Casper/Mac administration get a little hung up on the whole packaging bit when they first start out, so reading up on best practices and some do's and don't's may help you avoid unnecessary heartache later. (hint: you actually don't always need to repackage things; oftentimes installers just work as-is)

Lastly, once you've got a good handle on things, definitely look at some of the adjunct tools out there in Mac admin land, like AutoPkg, AutoDMG, AutoCasperNBI, mcxToProfile and others. There are a lot of great tools made by smart folks to help make some of the more abstract or mundane things much easier to deal with.

@mm2270 covered a lot of good things. I would also suggest jumping into the MacAdmin Slack channel. Ask questions. No shame in asking if your google-fu isn't working. There are LOTS of great MacAdmin minds that are willing to share.

I thinking a lot of good stuff as been said already: scripting, composer, and other tools.

But what I like to do along with that is read the manual. Like all of it, from start to finish. I do this whenever there is a new big version release out to make sure I stay on top of things. I find that some people are afraid of big manuals, but for me it comes easily.

Also, don't upgrade Casper just because there is an update. Determine what the upgrade provides and see if it's business critical for you area. Since we don't manage mobile devices here, I skip a lot of smaller upates that are focused for mobile devices.

I also find that every person has a time limit thing. So if I can't figure something out within X amount of time, I come here and ask. But make sure you try everything first before asking questions. Don't just come here saying, "I need a script for X". Come here having attempted to write a script for X and people will help figure out whats wrong.

Lastly, if you don't have an Apple developer account - it's worth getting. While I would never deploy a beta OS to the users, I find it helpful for testing to stay ahead of the curve. I can work with vendors to ensure that when the new OS is released, we'll be ready for it.

When it doubt - use the force.

Planning is the big thing I learned as a new Casper Admin. A number of people had admitted some 2nd thought in how they set stuff up or named things or in the policies/smart groups created. Another vote for scripting and Slack Channel.

The biggest suggestion that I can give is to set up a test environment which mirrors your production environment in every way possible. Test EVERYTHING in the test environment before implementing in production. Once you roll things into production, test with your test machines, and then roll whatever change out to IT staff first. Test JSS upgrades on the test box several times before attempting in production. We have saved ourselves a lot of grief by finding potential issues in test.

Learn and play. Take some, or all, of the courses offered by Jamf. Take other classes to expand your core knowledge. Read this and many forums out there to build on that knowledge.

Then play with what you've learned. Don't just do the job you're supposed to. Experiment, try new things, try doing something a different way.

Read

https://derflounder.wordpress.com

https://derflounder.wordpress.com/2016/02/11/getting-started-as-a-mac-admin/

Something that will come in handy for troubleshooting.
Create a smart group to be used in the exclusion scope for ALL policies and config profiles.
This comes in handy in a situation where you want to do some troubleshooting and want to specifically rule out all policies or config profiles from causing whatever issue you're experiencing (essentially, is the issue the JSS or something local on the computer)?

Make sure that smart group is populated with some dummy criteria that is NOT blank if you aren't using it. I mention that because I believe if a smart group is left blank (with no criteria) then the JSS automatically assumes you mean all computers. Read here: https://jamfnation.jamfsoftware.com/discussion.html?id=9434 and vote here : https://jamfnation.jamfsoftware.com/featureRequest.html?id=1659