It's hard to describe the feeling. It feels a bit like that time when I was finally caught and punished for doing something wrong, just a huge sense of relief.
1. Remove your phone from your person, but still keep it with you. I.e. if you carry a backpack/purse/whatever, put your phone in there rather than in one of your pant pockets.
2. For small tasks, leave your phone in your room. Obviously more difficult than the first item. In college when my friends and I would go to the servery to get dinner, I would leave my phone in my dorm room. This is truly immersive because it gives you no possibility of even wanting to use it when you are enjoying the time you are spending with the people physically present with you. (Again... clearly more difficult in our world today, but look for small opportunities; going to a coffee shop with a friend? Leave the phone in your car's glove compartment for that 20min coffee break.)