Captain America: Super Soldier

This is early on in Chapter 3 when you first enter the Bunker House. Push up on the d-pad, aim with the left trigger and click the Right bumper to select your targets. Once you have 4 guys selected hit the right trigger to throw the shield.Very easy place to get it since there are about 10 dudes just standing around.

If you find yourself later in the game (or all the way through!) and still need this achievement, you can boost it quite quickly using a combination of unlockable costumes, sewer access, and skill.
Just as Muzzer7 explained, you will need a full focus bar. To refill focus quickly, equip the "Classic Cap Costume" costume as depicted in the 1940s and 1950s. I am not entirely certain what the requirements are for this costume, but I unlocked it very shortly after acquiring my 25,000th intel point. It can be equipped from the main menu- EXTRAS - COSTUMES - Classic Cap Costume.

If you have already cleared the Estate level, all the better. Enter the sewer complex, then go to the Unlocked Door for Estate. It is in the northern area, second from the left in the line of 4 nearby tunnels.

When you enter the door for the Estate, you will move through a small hallway and up a flight of stairs before entering another hallway. To the right is a staircase in the center of the wall that leads to a wide open area. Inside this area, you can expect to find seven guards. All low level basic and ballistic guards, they dont possess too much trouble for you. You can expect five Kobolds and three snipers. One sniper is on ground level. The other two are up above, one to the left of the entryway and one directly above it.

Use whatever method you like to take out the kobolds. Friendly fire kills bring a bonus in focus. Use the LB deflection trick to swat sniper bullets back where they come from. You could use this location to boost your anti-sniper achievement, but chances are that you'll have that completed long before here.

Swatting the bullets back will result in friendly-fire sniper defeats, which boosts your focus. Because you're using the Classic Cap costume, you will receive even more focus than usual.

Once the room is clear, return to the sewer entrance. There is a slight load screen, then turn around, enter the estate, and do it all over again!

Rinse and repeat until you have your four full focus bars (you'll know because they will all be glowing and you'll see the Super Soldier RB+A message). At that time, follow Muzzer7's advice to target four and enjoy the show! If for some reason you dont get the achievement, its possible you only targetted three. If you have any focus remaining, you did something wrong. Thats okay, though. Simply repeat these steps, refill the focus meter, and try again.

You can also use this trick to boost your 50 Crippling Strike achievement if you havent already gotten it.

Good luck.

Have your special ability bar filled (all 4 blue blocks above your health) press up on the dpad to go into focus mode, select 4 enemies by pressing RB on all 4 of them, they will glow. then throw your sheild.

If you can only select 3 enemies because one is too far away or has just gone around a corner then back out of focus so you don't waste it

After you have unlocked the 'Prisoners of War' Challenge you can do this Achievement easily. Choose the challenge from the menu and start, easiest if you have already beaten the game and have all the upgrades/unlocks.

When you start there are a bunch of guys with guns, kill them.
If you kill them by deflecting their bullets back you gain Blue Bar strength.

Then go clockwise (to the left) around the circle (you can go either way really). As you do this you have the opportunity to make lots of "Perfect Timing" jumps. These jumps give you blue bars.

Kill the next set of guys on the other side and continue around the circle. Hopefully you are at 4 bars now. Keep making those perfect jumps and don't worry about the clock.

As you come around you will see a sniper off to one side from the main platform where the baddies have been spawning. Kill him and continue around to the next platform.

You should be at a little bit of an angle from the guys that spawned where the first group of soldiers had been. Using your Enhanced vision (up on D pad) and pulling the Left Trigger to zoom in, with your Right Bumper (RB) you should be able to target the four soldiers, 3 on the main platform and one on a platform below it.

Fire your shield, get the achievement.