Firstly you must identify your stutter. Understand what it is. For me personally, I block when I stutter. I feel my body tense and the word gets stuck in my throat. Identify the little things you do when you stutter (head jerk, lose eye contact, bite lip/tongue, etc.) Then actively practice to avoid these in a phone call while looking in the mirror. Call anyone! Family, friend, ordering food. Start on your own in a mirror and once you learn yourself and your stutter, you now have to work to counter your mechanisms, be it, maintaining eye contact, avoiding the head jerks, etc. The best practice after that is to practice with someone in front of you face to face. Find someone you can trust who understands you stutter and explicitly tell them, “Hey listen, you know I stutter. Can I practice with you and work on improving it.” Then repeat everything you did before (countering your mechanisms), but this time in a face-to-face setting! You will come a long way. Trust me, I have been doing it for a week and I already feel so much more confident about it.