Having finished the 4 movies on Expert here's some tips for playing on Expert.
- Find 3 other dependable players. Working in pairs or all 4 together is the key to surviving.
- Listen. Hearing any of the special infected and knowing where there coming from will save your ass. Personally I use headphones and can pinpoint the direction very quickly, even an incoming horde. Call it out to your teammates so they can help defend.
-Take your time but move quickly. Clear the random zombies standing around and search every room/corner. Have you just had a horde? They won't come for a while, get moving to the next point. Did you just kill the boomer and smoker? Get going.
While searching for health/bomb/ammo work in pairs. Call out which room/area you are searching. When entering a room, turn left and get against the wall next to the door. It keeps the regular zombies from getting you. Walking into the middle of the room leaves you open to attacks from all sides. Your partner will either be in the hallway or next room and can get there in a few steps. If a horde attacks, buddy up.
- Prepare. When you hear an incoming horde, get everyone into a small room if it's nearby. If you're out in the open, get to one spot and all 4 crouch together. If you hear a tank, setup the attack plan ahead of time. Who's going to throw the Molotov, which direction will the group run, does someone need pills/health to speed up their running?
- When fighting a tank (non finale) the best way is light him on fire and run away. He will die after 40 seconds once lit. No need to even shoot. One person should trigger the tank and have molotov ready, while the rest are a good distance away. Don't run backwards, you'll get stuck on things and the tank will get you.
Try to "kite" the tank. It involves having an object like a building or truck between you and the tank. The tank will chase you around, rather than over the object. Although the tank is faster than you, if you keep changing direction, so will the tank.
Auto-shotguns. These will take a tank down very fast even on expert. If all 4 survivors are grouped together and concentrate fire
When doing a crescendo event or finale, get your weapons ready and pick a spot to defend. The smaller the room/door the better.
Here are some good places:
No Mercy(NM)3 Crescendo - Skip it! Bash the door on the warehouse. This isn't VS, the zombies won't complain.
NM4 Elevator - Get in the closet. A standard tactic we all use on VS.
NM4 Early Tank - If you get a tank before you get to the cafeteria, retreat back to the first set of stairs and crawl under the landing, with autoshotguns you can kill the tank easily. Cheap tactic on VS but works great on expert.
NM5 Finale - Get in the closet next to the ammo. Use the standard 2 front crouched, 2 in the back shooting. When the tank comes, every get on the roof of that building and spot the tank.
Blood Harvest 3 - Have one person trip the train and fight the hordes from the top of the rail car. Even better, with some well placed pipe bombs, have 3 people standing near where the bridge collapses and get up there as soon as it falls. The pipes can be used to clear a path for the trigger person. You can fight the hordes as they come up the bridge.
BH5 Finale - 2nd floor of the barn with autoshotguns. No molotvs needed. The special infected always try to use the ladder on the left, the tank will go down in seconds. Easy finale.
Death Toll 3 - Inside church. One person on top of the piano. 3 in the corner near the door, away from the opening. If the person on the piano gets incapped, the horde can't reach the top of the piano.
DT4 Crescendo - Street. Have everyone get in the bathroom inside the building. The horde comes in a straight line for the bathroom. None of the should even reach it before getting mowed down.
DT Finale - The Rock. When in the house looking at the water it's to the far right. Crouch jump (not against the wall though) on this. The tank will throw rocks from a distance and throw them short. Once it gets to the rock it will try to punch and not climb. The only thing to look for is smokers who always come from the water around the dock. This can even be done only using pistols. With some pipes to clear the hordes as the boat arrives, this is also a great way to get the Untouchables achivement.
Dead Air Crane - Can actually be skipped. Climb on the spools/vent near the fence and get on top of the fence. Jump over the opening in the fence to the opposite fence. From there jump at an angle towards the corner of the opposite building where the container is still suspended by the crane. One of you way get the "hanging on the edge" knock down but as long as someone else makes the jump they can pull you up.
Dead Air Construction crescendo - Can theoretically be skipped but takes some skillfull jumping. Get on the railing facing the barricade. Jump onto the metal covers of the doors to your left. From there you can jump to a electrical box on the wall and over the barricade. Otherwise fight from the closet inside the construction space.
Dead Air Finale - Fight from inside the closet. Killing the tank is the hardest part.
Feel free to add better or different spots to help finish expert campaigns.