Listen, getting ready for Dead Frequency is actually pretty straightforward once you know what matters. You're gonna need that Ward Badge (this is crucial because checkpoints won't let you through without proper credentials), and make sure you've wrapped up "Like a Moth to the Flame" - there's no way around this one since it opens up Camp Icarus access.

For gear loadout, grab yourself a decent weapon setup - the PTM pistol works great, but really anything with good stopping power will do (zombies don't particularly care what you're shooting them with, but better gear means fewer problems). Stashing some extra ammo and grenades isn't a bad idea, because those device activation points can get pretty hairy with all the mutants showing up.

Something interesting - if you're running with Spark faction, you'll get access to some nice suppressed weapons which makes things smoother when you need to be subtle. And while you're at it, swing by Sgt. Batalov at Camp Icarus for some psi-pills (these help deal with those nasty psychic anomalies that pop up). Oh, and don't forget to pack some anomaly-detecting bolts, because those checkpoint areas can be pretty treacherous if you're not careful about where you step.