Getting this achievement is easier than it looks on paper and more consistent in comparison with Human Revolution, were some knocked out NPC's actually ended up dead.
The rule of thumb is to play the game with a stealthy approach, obviously with the appropriate build. Augs that focus on hacking, cloaking, awareness (Smart-Eye, radar augs) and accessibility (Leg and Hand Prosthesis) will offer you the chance to take the less travelled road and encounter the least enemies possible.
You want to keep your encounters with hostile NPC's to a minimum, since then the chances of you accidentally killing someone will drop significantly. Throughout your playthrough you should be patient, using cover and the Glass Shield as often as possible. Consider upgrading Jensen's batteries since your available energy at all times is the basis of this kind of playstyle.
Your go-to weapons will be cqc takedowns, the Tranq Gun and Tranq Rifle. The Rifle is actually the most useful out of the two firearms since it can be used from up close too. Personally I got this achievement using that one only, even though it has a scope that's supposed to not be convenient up close.
The last "tool" that you'll need is frequent saving. This is crucial to avoid voiding the achievement, since at the slight suspicion that you've killed somebody you can easily reload and try moving on non-lethally again.
If the non-lethal style is not your thing and you're struggling early on, focus on the Main Missions only. Side Missions may give you additional XP (and therefore more Praxis kits), but after a point the become a liability, especially after completing a good chunk of Main Missions and
To sum up, do a stealth build, play stealthily and patiently and save often.
Please note that you need to be immediately responsible for somebody's death to void the achievement. Shooting, stabbing, blowing up and dropping people off balconies will void the achievement, but hacking Sentry Bots causing them to turn them against the enemy will not void it.