Can anyone recommend a 101 guide on zombies mode? I've never played any of the previous CODs that had a zombies mode and I'm not sure I'm doing it right. I have questions like, why should I open the gate instead of just staying in the first area (well, I answered that one pretty quickly by getting overwhelmed with enemies after a few rounds), and are there objectives I should be doing?
I try to do rituals ASAP so it's easier and I can Pack-a-Punch faster. I also get Juggernog in early rounds too.
1). Open gate immediately, turn into Beast and shock the quick revive, melee the steel door, melee the box in the back of the pickup, go through gate and shock the construction crane, turn around and hook onto the stairs above then follow the path and shock the stairs. Grab the Pen by the construction crane and the summoning key in the back of the pickup. Proceed up the new stairwell and activate the ritual in the room. You don't need to kill the red men, just survived for a while.
2). I like to find where the Random Weapon Box is and go there first and do the rituals for them. You can find youtube guides for each section's rituals (I used MrDalekJD).
After the weapon box, I do the area with the best perk available. You will find broken, colored bottles outside each area's gate: red is juggernog health boost, green is speed cola reload speed bonus, yellow is double tap rapid fire.
The Rocket Shield is also a great tool/weapon in addition to the Civil Protector as Valar said. You need 3 pieces which can be found in each district (usually in upper staircase areas). There are workshops you can use to build it once you have all parts in each area.
Once I'm done with all 4 rituals, I "train" in the Pack-a-Punch room. I've survived solo to level 25.
3 foot shots then knife for max $$$$. Always save 1 or 2 zombies so you can do what you need to. Round 2 is 4, round 3 is 5, etc.
Edit: Segment next has some good guides on what things do and general info.