Few writers I know want to think about query letters, contracts, or pricing policies. They just want to write, get published, and maybe earn some money. Making the shift from literary to commercial is a complicated task, one that can be extremely difficult. In order to succeed at making money, a writer must remember a few principles.
First, don't undervalue your product. If the skills you have were so common, your clients wouldn't need to hire you. They could get any old hack, or just do the work themselves, which is often the same thing. They have chosen you because they need quality—and quality costs.
Consider hours spent on the job. I know you're not working for an hourly wage. Your product is much more valuable than that. However, if you have trouble knowing what to charge, analyzing the time spent is a good place to start. Ask yourself, “How much time will this take. What do I want per hour?” Do you really want to ask $50 for a job that takes you all day? That's like earning $6.25/hr. Surely you're worth more than that.
Don't overcharge. Like any business, you have to be competitive. Unfortunately, there are a lot of other writers out there willing to work for $3/1000 words. While you shouldn't stoop to begging, you have to charge an amount that buyers can afford. Be honest with them and charge a fair rate for the product.
Advertise. Website, business cards, Facebook page. All these things are great. You can find jobs on freelance websites like Elance, Freelancer, and Guru. You can even find a few on Craigslist. Personal networks are indispensable. Don't underestimate writing for friends and family who may own businesses or lead non-profit organizations. Word of mouth is often more powerful than expensive commercials.
Manage your time. As with any business, you have to weigh the value of tasks and prioritize. If you find yourself getting distracted, turn off your cell phone, close the drapes, even disconnect the internet from your computer if you have to. Do what it takes to be productive. Then set aside time for things like family, prayer, and exercise, because those are the things that energize and improve your writing.
Finally, keep working on what really impassions you. While building your network, completing jobs, and fostering your business, don't forget to work on any spec projects that stir your heart. Novels, screenplays, and stageplays can make more money and draw more attention than other types of writing. Anyway, spec projects are what we really care about. Let's be honest. We write for the stories, not for the money.