ULTIMATE GUIDE TO DMZ.
If you're a beginner who doesn't know how to play "Warzone DMZ", or an expert looking for ways to improve, this video covers it all.

00:00 Introducing everything you need to know
00:20 DMZ Faction Missions Explained
01:18 DMZ Contraband Explained
01:58 What happens if you die in DMZ?
02:34 DMZ Insured Weapons Explained
03:53 How to unlock more Insured Weapons in DMZ
04:09 Extra extractable loot in DMZ
05:12 How KEYS work in DMZ
06:00 What happens when the time runs out in DMZ
06:50 DMZ Contracts Explained
8:17 Optional objectives in DMZ
9:07 DMZ Strongholds Explained & How to get Stronghold Keycards
9:56 DMZ Weapon Case Juggernaut & Rewards
10:48 DMZ Random Events Explained
11:22 How to repair vehicles in DMZ
12:15 Faction missions: Make Contact, Locate & Scavenge, Al-Qatala Informant
12:30 DMZ Storm the Stronghold Guide & Walkthrough
13:15 Find a bigger backpack in DMZ
14:02 How to get EXCLUSIVE DMZ WEAPONS in Multiplayer & Warzone
15:20 Where to find the Chemist to get M13B in DMZ
15:49 DMZ Expert Secrets
17:16 20k XP PER EXFIL in DMZ
18:35 The Future of MW2 DMZ Mode

BONUS TIPS FROM HELPFUL PEOPLE IN THE COMMENTS:

1) Not ALL keys go to a door. Some keys go to smaller items that are loot caches themselves (example Ive personally found was a key to a locked toolbox within one of the areas).
They also tend to give a coordinate in regards to the grid on the map for the tougher to find ones! (Example: stone warehouse not an actual locked area G-2) - @BooDoop

2) You can still used the insured weapon after the first game. It only makes it contraband AFTER you exfil. So you loose it if you die after the initial game and have to wait the 120 minutes before you can build it again - @No_Sunscreen

3) The train has paper thin walls, and enemy AI will murder you while you’re on it. Be careful! - @Head of the Herd

4) Team up with some solo players - we were a squad, and found a solo player that didn't immediately shoot at us - invited them to join our squad (using the command wheel), and they accepted. So we were a squad of 4 rampaging accross the map, and helping each other completing missions! - @Sploftey Loftey

5) One more exfil...the "hostage rerscue mission" lets you discreetly exfil in the helo that comes to pick up the hostage with only your team seeing the exfil lcation on the map...good option if you have good loot your trying to get out with. - @Deadbird