Act 1 - "Hunted":
After running into the basement to avoid the helicopter and enemies, go upstairs and kill the 3 enemies that enter, then head outside. (The house on the right contains intel #10 on a table, the first of 2 in this level) Before Cpt. Pierce finishes talking, continue running down the path and around to the right of where the intel was. Stay there while two attack dogs come after you (if you stay back where your team is, they will kill the dogs too quickly) and let once jump onto you. Wait for the quicktime action to press
or whatever you have the knifing action assigned to. You will snap the dogs neck (poor doggie!) and the trophy will pop.
Feel free to ask any questions, and add me on TT/ TA/ PSN/ XBL as Danokitty. Happy hunting!