The number one rule for ignoring what people think, is to ignore your surroundings.
Now, imagine yourself in an empty room.
There are no people. There are no faces. There are absolutely no worries.
Just concentrate on something else, such as a car.
You don’t care what the car is thinking, you don’t care whether or not the car likes you or not, are you? (Don’t worry, I seriously doubt that the Peugeot 206 you’ve been staring at for the past two minutes is going to re-enact a scene from Transformers)
Oh, and you should acknowledge some of your surroundings, otherwise you might become victim to a car accident.
The reality is, people don’t analyse you nearly as much as you analyse yourself. Depending on what anxiety or depression you have (I have partial social anxiety) caring what people think when you walk in the room or become the centre of attention is quite a big deal. So, rather than observing, think of something else. It could be, what you’re having for lunch or whether or not you should ask out your love interest.
don’t care about what the people around you think, care about what you think.