This is for commercial photography - so if that is not the direction you want to go in, this may not be the most relevant for you.
I started as a photo assistant in 2007 and by 2009 had some of my first clients (they were hand-me-downs from the photographer i was assisting). I kept working at it and ended up taking to "part time" photography jobs that I found on craigslist. Both of those put me in touch with various people. I always made a point to give them my personal business card in case they ever needed photography services in the future.
If you keep handing out your business card, and keep your website updated and looking professional, eventually people will come to a point where they need photography work, and if they have your card they will call you. Then it is up to you to keep them interested in you by delivering great photos, and a great customer experience.
It isn't a fast process for most people, just to be honest. I lived on peanut butter and jelly for several years, and had no money to do anything other than paying bills. Eventually if you are committed enough to it you will reach a point where your name is known by enough people and some will use you for multiple jobs.
In addition you can typically find a local chapter of ASMP or WPPI and get on their assistant or photographer list. No guarantee that you will get work from it, but I got one or two jobs from that.
Over time, the more you do jobs for people and leave them feeling that they got a good deal, the more they will tell their friends about you when they hear they need photos.
if you are doing wedding photography or family portraits, the process is similar, only you can really market yourself to your friends and family first, and then to everyone you know and then to everyone your friends/family know. Get on Facebook and don't be shy about promoting yourself there. Take business cards everywhere you go. Almost everyone needs a head shot or a family picture at least once a year. if you are the last person they spoke to, you will be the first one they think of, so stay at the top of their mind.
Hopefully this is helpful!