Zombie Apocalypse: Never Die Alone

Alright, this solution is to tell you the best way to do particular objectives in the game.
There are several kind: Point-based, time, pwnage, hazard, survivor, kill-based, and unique. Here are some basic tips for each.

For all point based challenges, the key is the multiplier. First off, rescuing survivors is helpful as they add x100 to your multiplier. You need to kill with your guns as your zombie bait does not add to the multiplier. Resist the urge to use the C4 teddy and instead use Def Moneys Boombox bait as it will give you a second to regroup. Also do not use explosive pick up weapons as they also do not add to multiplier. Def Moneys pwnage is a major help. Each kill is worth +x5 as oppose to gun kills being +x2. You will lose multipliers if you are grappled, vomited on by Sheriff or sorority girls, or taken down (including being tackled by construction workers.)

For time based challenges you have to get through each level in a set amount of time. Dont worry about this one so much on the first run through. Learn about the level. Where your allowed to travel and when you're forced to stop and kill everything in the area. I've found it easier to take survivors with you or make sure they die. If you simply run past them they may hold up a zombie that you then have to run back and kill in order to proceed. Just run and gun and save your pwnage for the Damned enemies, (Except for Father Bills as it is easier for you to run around when activated and Def Money's as it mostly slows you down if you try to use it.)

Pwnage challenges are kill based so in order to use your pwnage you have to get that player enough kills to activate it. Usually this is done faster when you play as them, but the computer will build it up as well when it is AI controlled.

Hazard challenges are where you must kills zombies with a hazard by knocking them into or around it. Pretty simple.

For survivor challenges you have to rescue a set number of survivors. Usually there are more than what you need, but if your having trouble your best bet is to use Jeremy or Def Moneys bait to get the zombies away from the survivor before they die and grab them by rapid tapping A to calm them and get them. Dont worry about friendly fire if you see a survivor surrounded. Drop them off at the green ! located further in the level. For the last level, We're on a boat....., the survivors come after you kill the last boss (the fisherman) and will run towards Def Moneys yatch. You have to protect them and make sure they make it into the boat. (There have been some people that say it glitches occasionally and will not let the survivors go into the dock that leads to the boat however if you get more than one to that area they will knock each other into the boat basically.)

Kill based challenges require you to kill in some special way in the level.

Unique challenges are the quirky little challenges added in some of the levels that are out of the ordinary. These are usually a bit of a pain.

In the next section I'm going to go into details of each level for objectives that I haven't covered above. If I do not cover one you are having trouble with and the basic tips above are not helping, please leave a comment and I will try to assist.

Level 1: Main Street, DOA
Kill 15 Zombies in the first 60 Seconds - This one seems a bit buggy. Your best bet is to run full tilt through the level with a character with a powerful weapon to kill as quickly as possible. You will likely have to kill more than 15 (I don't know why, but that's what happened for me.) You must also know that it has to be YOU that kills someone, not the AI (the points from your kill will be colored and AI kill points will be white.)
Take No Damage - This is easier than it sounds. Just use Father Bill or Jeremy as their weapons are fairly strong right out of the gate. Keep on the move and do not let anything behind you. Use the C4 Teddy Bear liberally with a crowd to keep risk low.

Level 2: New Sheriff in Town
Get 15 Zombies Dancing - Just wait until there are plenty of zombies and use Def Moneys zombie bait.
Kill 20 Enemies with the Flying Donut - The donut is in the upper center of the map, it is automated so you cannot control when it will be fired. You best bet is to lure zombies over and then boombox them and let them get hit or just stay up there the entire time and it will likely pop.
Kill 10 Enemies with the Street Sweeper - Located on the bottom of the map, the street sweeper is on its side and you must knock zombies into the underside. The easy way is to stay up top til they spawn then move under the sweeper and pop rounds into them, knocking them in.

Level 3: Tarmac Attack
Take No Damage from Sheriffs - This is really the only challenge that takes a bit to complete on this level. The Sheriffs are the big gas spewing zombies and they appear in two places. The first time there are two Sheriffs and after playing through the level once you should remember where they are. You CANNOT get gassed. You're teammates can, but just to be safe I would not switch players during your fight. Your best bet is to dodge around and use pwnage abilities, Jeremys X4 damage is great for this. The second showing of the Sheriff is a pain. There are a lot of zombies. However, if you have the quad damage and a few C4 bears you can do this, just remember to move and not get gassed. Occasionally you will get trapped just try to stay away and use the quad damage to take em down.

Level 4: Change in Itinerary
Kill 10 Mechanics with Alma's Rifle - The Mechanics are the suicide bombers that run at you to explode. There are plenty here, so this shouldn't be too hard. Try not to use the boombox as if they are standing still, the AI will likely get the kill.
Kill a Homeless with the C4 Teddy - The homeless are the zombies that seem to teleport and yell "Change" and "Need bus fare" When you hear this, just throw a teddy and it should nab at least one of them.
Grind up 20 enemies in the Turbine - The turbine is on the right side of the map. Just try to lure zombies in there and pop em. If they are being problematic. throw a teddy past the turbine and shoot them into it before the explosion.
Kill the Baggage Thrower Using Jeremy's Pwnage - The baggage thrower is the Damned zombie that blows up the plane. Simply save up your pwnage for this give it a second or two of shooting then trigger it and light him up. Don't throw a bear as this means less targets for your squad so they're more likely to kill him then.

Level 5: Undead Double-Wide
Light 40 Enemies on Fire - There are two flamethrowers to use in this level. Simply grab them and spray a quick burst onto the zombies. Conserve the ammo as much as possible. If you don't get it after the last Flamethrower is gone wait for it to come back and then try to finish the job.
Kill 15 Sorority Girls - The sorority girls are the zombies that stagger around drunk and puke everywhere. All you have to do is kill them and there are plenty, but again it's best to use the power characters so it's both easier for you to kill them and harder for the AI.

Level 6: Death of the Party
Score 7,000,000 points - This bears special mention as there are a lot of possibilities for your multiplier to be reduced to nothing. Keep an eye on your team members. Rescuing them is your first priority. Also, learn where the health is in this level. Try to save the pwnage abilities for the damned except for Def Moneys.
Kill 20 Enemies with the Neon Sign - Located on the top of the map, it triggers every few seconds so just stand to one side and let them spawn then switch sides. Do not shoot them as it will then not count.
Don't Get Hugged by Grandma - The Grandma zombie is the Damned that appears at the end. Simply stay moving and don't switch characters, if you switch to someone that is in mid hug it will count against you. Watch out b/c sometimes she pounces. Pwnage abilities will make this fight a lot easier. Note: You cannot damage her when she is hugging someone.
Kill 50 Enemies with Bessie the Bull - The bull is in the center of the map. This hazard is triggered by shooting the bull. When there are zombies near just pop a shot into it and it will spin and kill them. It will need a few seconds to recharge but just repeat until finished.

Level 7: Energy Crisis
Kill 15 Enemies by Knocking them off the Scaffold - You can do this one of two ways: Throwing the teddy off the scaffolding (however you will have to kill a lot more than 15 normally) or use the melee attack to knock them off. If you do the latter of the two, use the boombox to keep them still them shove them off.
Kill 20 Enemies with the Modified Flare Gun - The Flare gun is located about halfway through the level and is basically a rocket launcher. Just conserve ammo for big groups (there are many of those,) and fire away.

Level 8: Shocking Conclusion
Take No Damage from Lumberjacks - The Lumberjacks are the large axe wielding Damned. They strike the ground and send out damage in a three point pattern. Just stay behind them and let them have it.
Take No Lightning Damage - The lightning comes from the towers after you start to press the buttons. Just make sure you avoid the lightning (AI characters can take the hit.) There is enough room to go around the edges of the platforms and not get hit.
Kill 50 Enemies with Lightning Damage - This one can be a pain. Immediately start the lightning up by pressing all three buttons then draw the zombies towards one of the towers by standing next to it. Once a sizeable amount have gathered, throw a boombox and bail or just sit there and take the hits if you don't have one.

Level 9: Thar She Blows!
Kill 30 Enemies with the Nailgun - Pretty easy. The Nail gun is the first weapon you come to. Just use it on the crowd that gathers as you come to that point and you should get it. If not, wait for the respawn and get it again.
Kill 20 Enemies with Father Bills pwnage - All you have to do to kill with Bills pwnage is stand near zombies. So just use him a lot (nailgun really jumpstarts his pwnage) and after activating it just into a crown of zombies.

Level 10: We're on a Boat, Mother$#@#er!
Kill a Damned Using a Melee Attack - Wait until you get a Lumberjack then just continue to melee him. You can use Jeremy's quad damage and that will help. Most times if you are meleeing a Damned and he is the only one left the AI will stop firing. Take the time to level up a characters melee weapon. It doesn't take long or cost much and it will help out a lot with this. Don't try this on a Grandma. They're invincible when hugging and jump around a lot. It's a pain to deal with.
Kill 35 Zombies in the Propeller - The propeller is on the right side of the map. Simply wait under and to the right of it and pop shots off or use the teddy to draw zombies to it. Very simple.
No Player is Downed - I saved this for last because it can be very difficult. The last boss can rip through your health quickly and every player counts for this. Even AI controlled characters. So if ANYONE goes down you fail. Couple of simple points to make when trying for this. Use your bait as it will keep the zombies the hell away from you. Quickly build up your pwnage with the nailgun so you can take the damned when they show up and keep Father Bill ready to heal. Keep an eye on your health. There are a lot of health pickups in this level if you can find them. If you cant take the grenade launcher and fire randomly into the barrells and boxes until you do. Use these health pickups well. If any player is below half health, it's time to use one.
The level goes as follows:
Zombie Horde
Lumberjack & Grandma attack
Zombie Horde (mostly sorority)
Lumberjack & Sheriff
Zombie Horde (w/ suicider mechanics and construction workers)
Two Grandma attack (after these die the flaregun will appear on the bottom of the map)
**Here you should make sure that you don't use Almas pwnage and have either Jeremy or Father Bills still ready to go as you can recharge one of them in the next wave.**
Zombie Horde (more construction workers and knife throwers)
Lumberjack Attack
After last zombie is killed the Fisherman and a Lumberjack will show up with the zombies.
**As soon as you see the Fisherman, fire up Almas turret, then Bills healing power, then Jeremys quad damage. Focus entirely on the fisherman as he is the biggest threat. Throw a teddy bear at most but otherwise stay on him and he should fall quickly. It bears mentioning that if you cannot do this at first, level up then try again later as it will probably be easier then.**
After you beat the Fisherman the credits start. You must not go down now either or you wont get the objective.
You don't have to save the survivors just live through this and it isn't that hard, there are not special zombies or damned just a few regular ones. after that you should get the objective

NOTE: If you are playing in a MULTIPLAYER game where YOU are NOT the HOST and your LAST OBJECTIVE is on the LAST LEVEL then DO NOT get it. If you're not the host the game boots you after the credits and last video are done before the results screen shows up therefore you get the objective but not the achievement. This has happened for more than one person, but is not garunteed to happen every time. If this does happen to you, play through in either your own multiplayer game or single until you reach the end. This worked for me. You can also try to get the last objective again in your own game. That has worked for a few people I know of that have had this happen. If that doesn't do it, you may need to delete the game and start over. I know it will suck, but it seems to be the only other way.

If you have any questions or comments please feel free to post them up.