The achievement really isn't that hard to obtain and will most likely come naturally. You must come in 3rd place overall in a ranked match. (Which means, the 3rd highest scoring player of both teams combined). For those that are having trouble. I recommend you play Squad Rush as it is a 4 on 4 game mode. Effectively increasing your chances of getting it.
Always be in a full squad.
Play as 'Assault' class and be sure to unlock the Defibrillator
Revive team members whenever possible for easy pts.
+100pts Team Member revive
+110pts Squad Member revive
Always throw Medkits in high traffic areas for healing pts
+20pts Team Member heal
+30pts Squad Member heal
If attacking, destroy as many objectives as you can in the match. M-COM stations can be worth up to 600pts each.
Keep checking the scoreboard to see where you stand.