I'm not talking about pro bono work. I'm talking about barely breaking even on existing client work. You can make the most beautiful design work in the world and run yourself right out of business. Here's how.
Bill different rates for different clients, based on how much you like them. Sure, give that classy nonprofit a hefty discount. And that referral you got from your sister, cut them a break too. Pretty soon, everyone's getting a deal, and you're bleeding money. Keep a consistent rate structure and you'll be protected in case of emergencies. Don't bill clients like you're running a retail store. You aren't selling a product. You're providing a service.
Give little extras away for free on every client project. It wasn't in the contract, but it'll just take you a few minutes, so why not make that sticker? And if they need changes to it along with a quick little one-sheet, that'll take only take a half-hour, right? There goes $1,000 out the window. Every time a client asks me for something gratis, I have to weigh the value of the work they've requested against the long-term value of the work we're contributing to their business. With rare exception, extra work always requires compensation. Otherwise, your client will expect the Mercedes-Benz luxury treatment when all you've got is a Toyota hatchback to offer.
Be a killer designer, but don't keep up with technology. Assume that every three years, the technology landscape will change dramatically. Browsers evolve. Markup standards change. Printers upgrade their prepress systems. Software vendors change the fundamentals of their interfaces. Not knowing your tools and implementation methods, or not having a strong support staff that can keep you up to date, can cause you major strife while you're also trying to get out the work. It also plants fear in the hearts of your clients and is a big risk factor for retaining business in the long term.
Do spec work to land every project. Rule of thumb: If you can afford to give away a week of work for free in order to land every new project, you probably shouldn't be doing spec work. You should be taking a vacation due to your extraordinary wealth. Or, as is more often the case, you should be scrambling to improve your cash flow by closing new-business opportunities that only require proposals -- and fewer flaming hoops to jump through. Besides, those flaming hoops usually set your clothes on fire and then you need to run around in circles, waving your hands in a panic until help arrives...