Beginners should focus on how to make a little money with freelance writing.  Those more confident in their writing and freelancing abilities, should already know what I'm going to say on how to make a lot of money in copywriting.

To make a little money in freelance writing, do the following things.  In order to make this brief and useful, I've skipped obvious items, like "know how to write," and "own a computer," and "deliver what you say you will."

1. Use the freelancing sites.  I won't recommend any of them in particular - use Google to research each freelancing venue you find.  Make sure that "companyname scam" and "companyname complaint" don't bring up any stories that scare you.  Once you've done that - you have found a place to do business, get paid, get organized, and resolve conflicts.
2. Prioritize your bidding.  When you are working on gaining new customers, no matter the venue, prioritize your bidding according to how badly you want each job.  This means, price yourself so that you are capable of getting work, according to your reputation and portfolio.  If you're in a venue where nobody works for more than a penny a word unless they've got serious clout, then, bid that.  Sorry.  Once you're able to discriminate, give discounts to the prospects you really want badly.  You should be reading the reputations and even Googling for extra background data on every potential client, by the way.
3. Oversell.  You have to do this, because proper communication during a job causes delays.  There will always be times where you have a job, but you can't work on it at the moment.  That is the time that should be spent selling the work you'll do next.  On the other hand, there's nothing wrong with having two or three writing jobs all at once, so long as the deadlines are reasonable when put together.  If you have less writing work than your capacity, do a little selling the next time you get lost for creativity.

To make a lot of money as a writer, do some of these.