Dog tags appear on fallen comrades that you will encounter in side missions, through exploration, and the main story. Obviously, be sure to loot their dog tag prior to leaving the area after finding them or killing them. Take note, that the fallen comrades are always near a burning red flare. If you see a flare, you know there is a dog tag nearby. Simply travel to the marker and collect the dog tags. The final two will not be given to you until after picking up the GPS tracker on the stage. Despite being technically missable, due to the fact they are given as side missions makes this a very hard achievement to miss unless you deliberately ignore them.
Make sure you finish this before going to the Mayors mansion to avoid another playthrough.
1 - Near the entrance to the subway at the beginning of the game
2 - First side mission in sunset hills
3 - West end of the northernmost bridge
4 - Helicopter pilot/part of story
5 - In back of the strip club in South Almuda
6 - Southern gas station in South Almuda (near Charlie's supplies)
7 - Small Chinese park area just off the highway in Southern Ingleton (appeared while driving the APC in the story)
8 - Outside yoga studio in Southern Sunset Hills
9 - In the street in the southeast corner of Central City
10 - The rodeo drive type area in western Central City
11 - On the southernmost bridge between Almuda and Central City.
At #1: I'm having the same problem...I found the dog tag but the "locate Haverman" mission isn't going off the screen, as if I didn't complete it...Haven't finished the dlc yet so not sure if I'll wind up getting the achievement. If you wanna find his body it's in the lower right hand corner of Central City, in front of the hospital
Just an update: found the last zombie squad member and I did get the achievement even though the Haverman one was a little glitchy. At #2: I don't think the alive members have dog tags, I think there's only 2 of them living and I don't remember getting tags near them
Check out this video guide for all 12 locations of K.I.A. Squad Members, the guide is complete with map views, and time links in the description to skip to whoever you're missing. The possible complications with locating Haverman are also explained, hope it helps!