I don’t think you can ever make ‘sure’ as some things are just out of your control. What you can make sure of is the things you can control like your notifications. I turn mine off. Facebook, Instagram…and silence my phone. I set a timer and have a notepad nearby. Ever time I get interrupted I write it down. At the end of deep work I than consult my notes and put a strategy together on how I can change or avoid that particular distraction. I have a butterfly on my door which signals to everyone that I am working and need my space.