Brink

Firstly, let me state that I spent many hours of stress trying to configure the easiest and best solution for this. Hopefully, with this solution it will be a lot less stressful for you.

Secondly, make sure the character you're using is of a low level, or create a new character. This will keep your enemies abilities to a minimum.

You'll need to use the following settings from the Main Menu.

Freeplay > Private Game
Game Mode: Stopwatch
Play Mode: Solo
Map: Refuel
Match Settings > Match Duration: 30 minutes
Difficulty: Hard
Min Team Size: 4
Max Team Size: 4
Friendly Fire: Checked
All other settings can be left to default.

You'll now have 30 minutes to attempt this, rather than having to keep restarting the game when/if you fail to get it. Make sure the difficulty is set to "Hard". Your AI seem to be a bit smarter when it's on this difficulty level.

Start the game.

Upon loading, make sure your on the team of "Resistance". Now once the match has started, head straight towards the Command Post in front of you and change your class to Operative. Now make sure you change your objective to "Guard the Storage Depot" from the objective wheel and head towards the Storage Depot. It's now up to your Soldier teammates to blow up the door. Once they have, collect the Hydraulic Fluid and wait for a couple of your teammates to join you by your side. If they're 2 Soldiers, kill them and at least 1 will respawn as an Engineer.

Do not proceed towards the Aircraft Hangar just yet. You'll need to wait for the enemy to place mines. You'll know they have when you hear your guy announce it over the radio comms or by looking at your objective wheel (it will have "Spot Mine" as one of the objectives).

Head towards the Hangar entrance where there are 2 ramps which slope down towards the airplane. You'll often find that the enemy deploys the mines in front of the place where you pour the Hydraulic Fluid. I would try and avoid these ones as they are a little too close to the enemy respawn point and you'll find yourself overwhelmed with enemy fire. Instead, they should place mines on the small balcony, just as you go down the 2 ramps at the entrance. This is your best place to earn this achievement.

Make sure you have an Engineer with you and spot the mine by aiming at it whilst looking down your weapons sight. This will "spot" the mine. Now, run towards it and stand on top of it. This will arm the mine, but make sure you do not step off of it otherwise it will explode. What this does is sets a new objective for any Engineers on your team. The Engineer will no doubt go running off fighting the great battle, so cover him as much as possible by shooting at any nearby, visible enemies. You can take cover by simply crouching. Once the firefight has ended, he should come to your aid and defuse the mine. You'll know he's disarming it as he'll get his spray can out.

Credit goes to immikeulate over at ps3trophies.org for the original solution.

Using the single player method describer by Aesiwatt.

Once the mine is spotted, step on it.
Mines do not blow until you go OFF of them, so the engineer MUST diffuse it... They usually ignore you so you may be waiting a while unless you are carrying an objective or are the only class available to complete the next objective.

On hard A.I. are smarter so I suggest that on freeplay with as few bots as possible but enough that one of them will plant a mine eventually.

http://www.ps3trophies.org/forum/brink/106294-i-finally-conq... Appears to work very well.

*Co-op Solution*

Go to FreePlay, make the max 2, min 2, and turn off the balance for teams(so players can switch). With 3 friends just have one friend on the other team run to you and place a mine. Then, as an operative aim down your sights at the mine until the little bar fills and then its spotted. Then, have the other friend on your team(the engineer) disarm it for you.

First, make sure you are the operative class, and then find an enemy's mine on the ground. You can tell it's an enemy's because it will be highlighted in red at close range. Then, just open up your objective wheel, stare at the mine, and press the action button to make it one of your teams objectives. Alternatively, you can iron sight the mine which will automatically spot it. Now, you have to wait for an ally to come along who is an engineer, and he must defuse it.
Now the problem is that when in single player, and you spot a mine, the chances of your team mates actually disarming the mine is slim. They will usually just throw a grenade at it, or shoot it to destroy it. So it pretty much has to be done online. (And yes, boosting with 3 people does make it a lot easier if you're fine with that).
Cheers!

Two human player method.
Freeplay, private match, Aquarium map. Set the team sizes to 3 and "balance teams". When you start, you and your friend will be on opposite teams. Have the Resistance person change team to "spectator" then to "Security" (game won't let you change directly to "Security").
When the match starts, the person getting the achievement becomes an Operative and the other person becomes an Engineer.
Chill out until you hear Captain Mokoena announce that "the enemy has deployed mines". Operative goes to objective wheel (up on D pad) and uses right stick to set objective to "spot mine". You now have to visually sight the mine. They are normally on either side of the door to be blown, or nearby. To identify the mine for the engineer, aim at the mine as if you are going to shoot it. Squeeze the left trigger to zoom in. Done correctly, an orange bar will appear above the mine and quickly fill in. If you are in disguise, it is a little trickier because you can't see your gun sights, but the actions are the same. Once the orange bar is filled, the engineer can see the mine.
When the engineer gets close to the mine, '"x" to disarm' will appear and the mine can be disarmed.
Note: I set the team sizes to 3, meaning I had one bot on my team. There is a possibility that my bot ally will trip the mine, but I figured that one extra bot on my side was manageable while having 3 enemy bots gave them a better chance of spawning an engineer.
Note: I have never gotten an A.I. bot to disarm a mine. I once stood on a mine for at least 5 minutes until finally an engineer ran up to me, planted our own mine next the enemy mine, and then ran off.

THIS IS THE METHOD IF PLAYING SOLO.

Its an adaption to 'thirtysmooth's method in the 1st solution except I did it with teams of 3-I got pissed off with soldiers throwing grenades at mines or just running into them so I thought lets just keep the number of guys to a minimum to reduce the chances of that.Ok so here's the deal:
Freeplay-private game
Stopwatch mode on 'Refuel'
Play as 'Resistance' Operative.
3 to a team.
time:30 mins
difficulty:normal-its up to you,i did it normal.
Friendly fire ON
1-As the game starts choose 'Destroy storage doors' as objective.
2-Once the doors blow off you get the hydro fuel-but don't move.
3-If one of your team isn't an engineer kill them-they WILL come back as one.
4-When the announcer says 'enemy mines planted'-change your objective to that 'spot mine'.This will mark it for you.Wait til your engineer is near you.
5-Slowly make your way to the highlighted mine,try to kill the enemies who attack you.
6-When you get close enough-spot the mine and crouch & wait.
7-If your engineer is close he'll say 'I'll get the mine'
8-Keep him covered/kill anyone else,even the other guy on your team,in the area-this is where having 3 a side helps greatly.
9-As soon as the threat of enemies are clear he'll spray the mine & you'll get it.
If it doesn't work the first time you've got 30 mins to try again & law of averages says you'll get it-TRUST ME-ALWAYS MAKE SURE ONE OF YOUR TEAM IS ENGINEER-IF NOT KILL ONE OR BOTH-THEY WILL COME BACK AS ONE.

Good luck!!