Grand Theft Auto IV/Assassinations

Once you complete Phil Bell's mission "Truck Hustle," you receive the "High-End Assassin" phone call. The Fixer directs the player to a payphone across the intersection of Odhner Ave and Traeger Rd in Alderney (Indicated by the Assassin's target icon). You can call the Fixer at any time (of course not while any storyline missions are active) and he will give you one of nine Randomly assigned jobs. Also of note is the fact that when the calls over Armor and a Mission specific weapon are spawned over the fence behind the payphone. (It's not required to pick these up, but its is helpful.)

Migration Control
The Fixer wants you to take out a target a top of the Booth Tunnel in Alderney City (more specifically the helipad). Grab the armor and RPG if you want and head toward the target. Once you reach the target open fire on the Helicopter trying to lift off. This is where picking up the RPG is extremely helpful. Once the helicopter is destroyed run up with a weapon and check the radar to make sure the red blip (your target) is dead. If not, well…you know what to do. You will receive a phone call from the fixer afterwards and get your reward money.
 * Reward: $1000
 * Mission Specific Weapon: RPG

Bailing out for Good
The Fixer gives you the assignment of a high-risk target at the police station in Leftwood. After you get the job grab the armor or weapon if you want and head over to Leftwood. The target is being escorted into a car. You can take him out them or follow them a while, but it's recommended that you take him out before he gets into the car. Because there are police around you are most likely to get one star once you start shooting at the target. Be careful to avoid killing the police officers in the possible ensuing gun fight or you will automatically get three stars and that's hard to escape from. You don't have to lose the police to get the call from the fixer giving you your reward money, but staying put could cause your wanted level to rise.
 * Reward: $1000
 * Mission Specific Weapon:

Derelict Building
Three men (your targets) have been lured to an abandoned building in Alderney City. Grab the armor and weapon if you want (this time it comes in very useful) and head over to the seven story building. An Alternate way to complete this mission is to heli-drop on the roof and work your way down. As soon as you enter the target area the targets and the other men there will open fire on you. The first target is on the ground floor but will flee to the basement of the structure. Take him and anyone else out and head up to the upper floors. Each floor has about two to three armed gunmen. It's not required to kill the non-targets, but it helps immensely to not have five people shooting at you. Use cover, first-aid kits, and the explosive propane tanks to eliminate them and the targets. By the time you kill the second target you might receive a star because of all the shooting. Your mission is complete once all three of the targets are dead. Like always, you'll get a call from the fixer and get your reward money after they all lie dead.
 * Reward: $1000
 * Mission specific weapon: Grenades