A Lot Extra Achievement GuideText Guides are complete so If you have any questions feel free to leave a comment and I'll get back to you ASAP. If you leave a negative vote please let me know why. I will be making Video Guides to some of these within the next 24 hours.
The
A Lot Extra achievement is earned by completing all Bonus Objectives throughout the 12 mission story line. Below are all the Bonus Objectives to each of the 12 missions that you must complete.
Mission 1: The Signal*** Spoiler - click to reveal ***Objective: Kill five Grunt squads with Warthog Ram.
After a cutscene you will need to escape to the extraction zone but will be swarmed by enemies along your path. There will be Grunt Squads along the entire drive there so press 
and charge at them to get the kill.
Mission 2: A New Enemy*** Spoiler - click to reveal ***Objective: Kill 30 infantry units with Hellbringers
When you get your base up and running create a bunch of Hellbringers from the barracks and send them around the map to kill 30 enemies.
Objective: Destroy 20 enemy structures with Hellbringers
Same as before! While exploring the area to kill infantry, destroy every building possible until you get 20.
Objective: Use Restoration Drones five times
You will get the drone leader power shortly after creating your first base. Once used it will require a cool down so use it, wait for the cool down then use it again.
Objective: Take out 10 targets with the Grenade special ability.
Once you have completed the Hellbringer objectives, create a bunch of marines and use their grenade ability on enemy units or buildings with .
Mission 3: Ascension*** Spoiler - click to reveal ***Objective: Destroy 20 vehicles with a Cyclops
When you make a base you can build barracks and create a cyclops. Now move them around the map and destroy vehicles while trying to ignore enemy squads. The best way to do this is to camp around the mini-base to the left of your base as it spawns vehicles.
Objective: Kill 20 squads with a hijacked vehicle
You will hijack a Wraith during this mission which you can kill a bunch of ground enemies after building your first base. Head north of your base and you will find the enemies big base where it will constantly spawn squads.
Objective: Destroy 20 vehicles using Hornets
Refer to the Cyclops objective.
Objective: Use the Archer Missile Leader Power three times
Capturing one of the 3 nodes will give you an ability point so use it to unlock the Archer Missile and use it 3 times.
Mission 4: One Three Zero*** Spoiler - click to reveal ***Objective: Kill three units using Spartan Slam
From where you start head over to the cliff face and you will see two groups of grunts below you. Wait until they are next to eachother then hit to slam on them. Once your ability charges again just slam once more and you'll finish this objective.
Objective: Kill the scared Grunt before he flees
Once you reach the another dome you will see two more Hellbringers locked inside the dome. Once freeing them you will hear Alice say “Heads up! Looks like we woke the neighbors!”, this indicates the sacred grunt is on his way. Once a grunt unit shows up focus all fire on it as it runs away and you will clear this one when they die.
Objective: Kill three units with Archer Missiles
You will get the Archer Missiles near the end of the level when you must survive the waves coming for you. Put Alice in one of the towers and when the first wave comes use the Archer Missles to kill them and beat this in one go. If you fail simply reload the checkpoint.
Objective: Kill three units with Lotus Mines
Pretty much the same as above but use the Lotus Mines on the second wave that comes from the left of the base. Put them in front of the enemies and they will walk over them and die. If they destroy them reload the checkpoint.
Mission 5: Cartographer*** Spoiler - click to reveal ***Objective: Kill 30 enemy air units using Wolverines
Very simple one to do. Make about 8 wolverines and leave some at the base and take some with you to the objectives. Once the shield is down you will have multiple sentinels attack your base which will rack up the number easy.
Mission 6: Lights Out*** Spoiler - click to reveal ***Objective: Complete the mission with all 10 squads of prisoners freed and alive
This is a tricky bonus, not easy to complete. You can simply leave prisoners behind after you liberate them, so they avoid combat. But that reduces the number of troops available to deploy in battle, because the freed prisoners don’t count against your Population cap.
As you navigate through the level, keep your Spartans and all other units out front, then direct the ex-prisoner group to remain in the rear. They can jump into the fray when you encounter foes, but you can group-select them instantly and pull them back if things get too hot.
Objective: Don’t let any units get destroyed in the capital ship bombardment zone
Keep units from wandering out into the blackened zone where Decimus calls down orbital strikes from the capital ship, Enduring Conviction. If a unit gets close, white targeting reticles suddenly appear, followed shortly by plasma cannon blasts. Stay clear!
Mission 7: From The Deep*** Spoiler - click to reveal ***Objective: Hijack a Locust
Locusts start lumbering up the main beachhead early in the invasion. Use Alice’s special ability to hijack one of these siege walkers. It’s nice to add its powerful focus cannon to your arsenal for a while.
Objective: Get 20 kills with the Scorpion
The more Scorpions you can make and get onto the field, the more this bonus takes care of itself.
Mission 8: Hold The Line*** Spoiler - click to reveal ***Objective: Kill five units with Turret Drop
One of your Leader Powers is Turret Drop. The Spirit of Fire rapidly drops a Turret from orbit with remarkable accuracy onto a spot you select. The gun emplacement is temporary, lasting about 30 seconds, but it inflicts serious damage to enemy units over that time.
Objective: Kill 10 enemies with the lightbridge
Late in the mission, you hear Anders report that the Banished have activated the area’s lightbridge, giving them a direct route from the north that circumvents the west barricades. Get an infantry unit to the lightbridge control console and use it to deactivate the bridge. But wait until several enemy units are crossing, because when the bridge disappears, they plunge into the chasm. You can activate and deactivate the bridge as many times as you want. Lure 10 units to their demise this way to earn a bonus.
Mission 9: Under The Dark*** Spoiler - click to reveal ***Objective: Kill 50 Banished units with a UNSC Sniper
Good micro’ing keeps Snipers alive. Maintain your distance from enemies to leverage the Sniper’s superior range and accuracy advantages. He can usually nail targets well before they can hit him back. A good tactic: fire and retreat, staying outside the target’s more limited range until the foe falls.
Objective: Use Snipers to sweep for 50 plasma mines
The Banished have planted cloaked plasma mines throughout this area. When deploying units, keep Snipers out front for their detection and long-sight abilities, and move in small “steps”—that is, advance toward destinations in a series of short movements instead of clicking far ahead. This way your Snipers can spot cloaked mines and shoot them from a safe distance.
Objective: Kill 30 Banished units with the Kodiak
Kodiak mobile artillery units can hit with fearsome power from great distance, but they can’t hit what they can’t see. Use cloaked Snipers to sneak close enough to enemy units to “spot” them (i.e., reveal them through the fog of war) for your Kodiaks.
Objective: Kill Banished units with an orbital strike
Bring up your Leader Powers radial and deploy an Archer Missile strike against the Brute Warlord and his clan. Depending on how many targets your bombardment destroys, it may take several deployments of this Power to complete the bonus objective.
Mission 10: The Foundry*** Spoiler - click to reveal ***Objective: Destroy 25 base structures with the Scarab
There are many buildings around the map which you can destroy pretty easily. Have your scarab focus on them and you will rack this up quickly,
Objective: Destroy 15 Blisterbacks
A number of these floating menaces are deployed along the access route. Don’t cluster units together, as Blisterback plasma missiles cause splash damage. Alice can hijack a few, but killing Blisterbacks earns the bonus.
Objective: Kill 40 squads with the Scarab
The Scarab can eviscerate any foe, but it’s particularly lethal to infantry. To boost its kill stats, keep the Scarab’s primary focus on enemy infantry to which there is plenty of.
Objective: Destroy 15 Banshees with infantry or Wolverines
Once you get a Garage built in your base, produce two or three Wolverines right away. This mission is teeming with Banshees, and you need good anti-air support at all times.
Mission 11: The Halo*** Spoiler - click to reveal ***Objective: Lose no more than five units to the Retriever Sentinel
Keep a sharp eye on the Minimap to monitor where the Sentinel Retriever is at all times. The big craft moves slowly, so if you see it drifting toward your units, you usually have time to maneuver them to safety.
Objective: Kill 10 enemies with the Vulture ability
If you’re at Tech Level 3, consider building two or three Vultures at your Airpad. Just one of these fearsome floating gunships can make the defense of control towers you’ve captured much easier. When Spirit dropships ferry in Banished raiders, use the Vulture’s special ability to fire Phoenix tactical missiles for quick kills.
Objective: Keep the enemy from acquiring more than 700 tickets
If you post a strong defense team at each control tower you’ve captured, you’ll deny the Banished any opportunity to gain Control Points (or “tickets”) for the amount of time they dominate a control tower.
Mission 12: Last Stand*** Spoiler - click to reveal ***Objective: Upgrade Turret deployment
You pick up decided tactical advantages as well as bonus points if you upgrade all your Turrets. In the two passages where you have a Turret on either side, upgrade one to an Anti-Infantry Turret and the other to an Anti-Vehicle Turret. In the two passages where only one Turret overlooks the entrance, upgrade each Turret to an Anti-Vehicle Turret. You complete this bonus when all six Turrets are upgraded.
Objective: Kill the commanders within 10 minutes
Your best bet for taking down the Brute Warlords early is to saturate their positions with Leader Power bombardment. Before you engage each Warlord, wait until all your offensive Powers (Archer Missiles, ODST Drop, Turret Drop, Lotus Mines) are charged up and ready to go. Send out a strong, Spartan-led group to attack the Warlord clan, then start dropping in all your orbital surprises.
Objective: Kill A Scarab With An Archer Strike
Very simple! There will be 4 chances to unlock this so bring in your condor and rain hell on a scarab and when its health is about half way, use the archer strike to kill it.