9. A Very Effective Way Of Avoiding An Alert Phase
Once you've bought the 'Social Engineering' perk, you'll be able to hack into peoples' phones to cause a momentary distraction whenever one of your 'hack lines' matches up, be it from Marcus, a drone, a camera feed, etc.
However, this distraction supersedes an alert bar filling up, so even if you've been spotted by a nearby guard, simply hit L1 and Triangle/Y to send a distraction their way, interrupting their "Huh, what's that?" animation and allowing you to run up for the K.O.
Be aware that you can't do this once a guard's status has gone yellow or red, but if you're quick, it might just save you tackling an entire base-worth of goons.