FAIL; I was trying to do this the hard way with Alien Grunts. It wasn't really working out because I would die so fast or there wasn't enough Aliens to choke in some of the missions.
Easy way of getting this is to replay the second mission "SECOND CHANCE" put the difficulty on Recruit so you can lolly gag around. Once you're outside you can see your first two victims from the rooftop. Now run up to them and hold the blue X button to grab them then hit RT (Right Trigger) to throw them then repeat with all the soliders you see throughout this mission. Should get the achievement after choking a few guys out by the yellow tents. Easy. :}