Smart Metering, step one.
Tie it all together, make it mandatory, farm it out. Eric Blair never in his wildest nightmares saw this one coming. It'll be under the guise of saving energy to start with, i.e. your IoT lightbulb isn't sensing any movement in that room so can safely switch off, not a huge saving assuming efficient LED, but fifty thousand of them doing the same thing adds up. Then you move on to appliances like washers and driers timing their runs for off-peak demand signalled by the meter, which people like because it's cheaper and automatic. All very sensible.
Then your 'fridge gets connected to a supermarket on-line ordering system which lets the do-gooders gradually remove all the sugar and salt from the stuff you like until everything tastes worse than the box it comes in, your telly starts recording stuff you watch most frequently (throwing the odd bit o' propaganda in for good measure when TPTB decide it would be nice, along with facial profiling to see what you react to the most) and your car uploads its geo tracks for the day to the road pricing initiative when the net goes quiet. Get them used to everything happening for them and, suddenly, they're paying no attention to what it's all actually doing. Slowly, oh so slowly, you lose control of your life.
Then you scrape the data and profile folks. Ker-fuckin'-ching, not to mention being a snooper's paradise.