Running the final dub mixer or the production sound mixer?
If the latter, what's expected of you is perfect, top-notch recordings from the set or stage with little to no need to go in and fix it later. Reason being is that time is not on your side to get it right. You're not going to have as much time as Terrence Malick gives his sound crew to get the sound perfect - if it's a talk-show type scenario that is either live or airing the same day, you have to streamline the editorial process to be as fast as possible (and with live, there is no second chance).
Couple things to read up on and have handy:
Wireless mics (transmitters and receivers. How to use them. How to debug them when they go bad).
Backups for everything. David Letterman has his main mic and 2 backups standing by should anything happen to the first. It's a good habit to have and a good motto is "If it doesn't have a backup, you don't even have a main".
RF spectrum analyzer. It comes in handy when it's 15 minutes until shoot time and your mics drop out due to interference. You can find affordable ones (that don't cost $8,000) like the RF Explorer.
Learn how to plant and hide mics and make them sound good. This one is tricky since you're never going to find a manual on the subject and there are as many methods and opinions as there are production sound mixers out there. Toy with it a lot, and find what works for you best and continue to figure out better ways to mic and record people.
If the scenario has a PA in the house where you are recording, become a very good friend of the FOH mixer and PA tech. They influence about 50% of your recordings with the PA alone. Make it your business to read up on and how to set up PAs and PA theory (line-arrays, point source speakers, what happens with low-end coupling with an array of speakers, etc.) and ask to be sent the PA design and MAPP it (Meyer Sound tool) before you let them hang the PA. When I do live shows like corporate meetings or lectern gigs, I always make it a point of seeing what type of splash or response on the stage I'm going to be getting from the PA, and I've had them re-design the PA to gain about 6 dB more headroom on gain-before-feedback for my mics. Then, when you go to final mix the show in post, it can be the difference between a difficult mix or a simple one due to how much PA is coming back into your mics.