I've been in the freelance game a year and a half, roughly. Three years if you count the time I spent working part-time. I have had phenomenal early success. By that I mean that I have more money than I need to pay my bills, I don't spend time looking for work, I choose which clients and even which projects I work on, and I turn down anything that doesn't feel like a good fit. I've reached the point most freelancers set as a goal for "success." So how did I get there?
Step 1: Be really good at what you do.
I know this can sound daunting when you're just starting out. You may feel like an amateur, only posing as a professional and completely without direction. I certainly did.
But I don't mean you should be really good at marketing yourself, or at keeping your books, or at tracking and prioritizing your projects. Those are the trappings of running a business, and while you do need to become good at them, you'll inherently stumble a bit at first.
But that's not what you do. That supports what you do. What you do is that craft that you sell. For me, it's writing and editing. For you it could be any number of things: baking, painting, doing taxes, sewing. It doesn't matter. Just be a master.
You might already be really good at what you do, even if you've only just started freelancing. Many people begin freelancing because they've been doing something they love for years, even decades, and they decide to turn it into a full-time occupation. If so, wonderful. Keep at it. You've mastered your trade.
If not, take some time to become really good before you strike out as a freelancer. Take some classes, or maybe even get a degree. Work as an intern. Volunteer your services for friends and family. Practice constantly. Show your practice work to people and get their input. Keep doing these things until you're really good. Master your craft before you sell it.
Step 2: Get really lucky.
This sounds horribly defeating, I know. Luck plays an unfortunately large part in success. But, like a Vegas casino, you can stack the odds in your favor to bring luck your way.
First, specialize. Do people want a baker, or do they want a wedding cake baker? Even more, do they want a wedding cake baker who makes masterpieces that look like a zombie apocalypse? The more specialized you make your craft, the more likely you are to draw a particular customer or client, and the more likely they are to pay you well.
You may protest, "But I like doing all sorts of things! I don't want to limit my work!" Well, who doesn't like doing all sorts of things? Specialize more than once. For example, I specialize in writing and editing primary and secondary science education materials. I also specialize in writing and editing sci-fi and fantasy novels and short stories. This doesn't mean I never write or edit anything else (of course I do), it just means I don't market myself that way or draw many clients who want other things. Your clients and customers have a very particular need, and they will feel confident you can meet it if you've stated upfront that it's what you do.
Second, tell everyone what you do. I mean everyone. Your hairstylist, your bank teller, your cab driver, your kids' teachers. You never know where your lead will come from. I got my first professional editing gig following a conversation with someone in a swimming pool at a friend's 4th of July party. Tell everyone.
Third, join a professional organization that matches freelancers with clients. Find a respected one in your field and pay whatever dues they require. Trust me, you'll earn it back. In writing and editing, I highly recommend the Editorial Freelancers Association. I get daily notifications about potential jobs. Two of those notifications were for clients who now provide almost all of my income. Again, specializing is useful here because clients who post job listings to groups like this are inundated with résumés. Yours will stand out if it showcases focus that matches the client's needs.
There may be other things that can help in specific industries, like building your website or attending conferences. Talk to successful freelancers in your industry to find out what they see as vital tools to finding clients. And have patience. For a while, you'll spend most of your time looking for jobs and clients. It can feel very defeating. Keep your head up. Your clients are out there, looking for you. Be ready when they find you.