I've got a very good strategy in Veruckt that always gets me to at least level 22.
First off this guide is for 3-4 people playing zombies.
Ok so to start off the M1 Garand side will be opening the doors. Let the 2 on that side get the courtyard while the rest are watching the back windows. When the 2 on the M1 side get at least 2500 points they should rush to the power room and turn on the power. The 2 people downstairs should buy jugernog and head upstairs. Now, have 2 people watching the stairs. These people will be prone on the top off the staircase while the other two cover them. They people watching the stairs should have shotguns and the people covering should have MG's. If things start to get too hard buy betties and fall back to the kitchen. Lay betties at the stairs and the power room (so you have somewhere to fall back to). So basically you do this plan until hopefully the mystery box moves, but if doesn't start doing my second strategy around wave 10-12 whenever it starts getting to hard. Make sure to have sleight of hand before you move. Now, at this point everyone run downstairs & buy juggernog and quick revive if you don't already have it. Now, open the couch on the Gewehr side. Have one person guard the window at the end of the hall way while the rest guard the whole in the wall and the stairs. If things get too hectic open every door except the 1 near the double-tap. Now, just camp here until you die.
*ADDED TIPS*
Get juggernog first then the rest of your perks. There's no point in buying perks if you can just get knocked down in 2 shots.
Try to keep one guy alive at the end of the level and have everyone repair and go to the mystery box.
Level 24-30 are the hardest after that it becomes very easy.
Teamwork is essential. Without it you WILL die a lot sooner.
Have the guy with the best weapons be in the front of the hallway and the worst guard the window.
If you do my strategy you can see when the zombies are coming if you look across the courtyard. This will help you know when there is time to reload.
Electroshock defenses will get you down please don't run through them.
To have a higher chance of getting a better weapon use the mystery box when the ? are the darkest.
If you have any other tips feel free to post them.
** Alternative Strategies**
I can only really explain myself by drawing these.
X......X X......DT
The X's represent people and the DT represents double tap. Have the guy with the best guns on the DT side. He will have the best weapons and preferably a Browning and a raygun. The guy to the left of him will be a support gunner and have high rate of fire guns that will quickly damage enemies. He should have a PPSH and any other MG they want. The guy behind him will be the medic and revive people. He will also help the guy at the window making sure he doesn't get overwhelmed. He should have at least 1 auto gun the best would be a ppsh but tends to run out of ammo to fast.
Alt. Strategy #2
| X| X| X| [ED] [W] X | |
Similar to the previous one but a lot easier. Have the guy infront in prone with an MG and a Browning. The guy behind him will have an SMG and cover fire. The guy behind him will be medic and help at the window and turn on Electroshock defenses. While doing this strat. the zombies will come at you in a straight line and easy to tack down. It is recommended that at least 1 person has a PTRS to take down the line of zombies.
If you have any strategies feel free to post them.
