Start With Your Sphere of Influence

Your sphere of influence, or SOI, is comprised of your friends, clients, former clients, family, etc. Anyone you know or knows you is part of your sphere.
The nice thing about your SOI is you've already made some sort of connection with them. It's easy to pick up the phone and tell them how excited you are about your new career. Take advantage of social media or you might even send them a post card, but your SOI is low hanging fruit. Your challenge is going to make sure they don't just see you as a friend, they now see you as an agent too.
I can't tell you how many times our new agents been disappointed when someone they knew fairly well bought or sold a home. When they asked why they'd reply "I forgot you were an agent or I would have called you".
Maybe they did forget and maybe they didn't. Maybe they were just nervous about letting you list their home but it's very important you keep subtly reminding your sphere that you're an agent now. That brings up another topic.
You can't just expect someone to give you their business because you're friends, acquaintances or even family. Real estate agents are everywhere. They might have had a great experience with another agent and they want to use them again. They may not even like you as much as you think.
When it comes to family, remember this, if you list their home and something goes wrong that might negatively impact your relationship forever. Something might happen that's completely out of your control but costs your family member money. They'll blame it on your inexperience and then the chatter begins within the family. No commission is worth that.
Throughout your entire career, you'll sometimes find yourself surprised and disappointed when a friend or relative chooses someone else to list their home. When that happens, and it will, don't dwell on it. You just have to let it go. They don't owe the listing to you and they had their reasons for going with someone else. Calling them up and asking them why they didn't list with you only makes you look entitled, petty, and confrontational.