You may not realize it, but as a contract worker, you are often the biggest influence on whether or not you can land long-term or continuously-renewing contracts. The ability to ask present employers for more work is a career-saving skill you can't afford to be without.
WHEN to Ask:
Ask when you discover an employer you enjoy working with. Don't let those good working relationships slip through your fingers. When you find an employer that you like working for, don't be shy about asking to continue.
Ask toward the end of a job, but not at the very end of the job. Don't wait until you've turned in a project or completed a short-term gig to ask for more work (though you are better late than never). Find that sweet spot, toward the end of the gig, when you've established a good relationship, but aren't yet out of work.
HOW to Ask:
Ask for specific work, don't just ask for "more." There isn't anything wrong with: "Keep me in mind if you think of anything." However, it's too easy for the employer to say "thanks and goodbye" in response. Good journalists are taught to keep a conversation going by never asking yes/no questions. By asking open-ended questions, journalists are better equipped to keep the interview conversation going. The same is true when a contractor is asking for more work. By suggesting an idea for another project, you are more likely to get feedback you can use to keep the conversation/relationship going.
Ask after gathering the knowledge to intelligently suggest a project that benefits the employer. This may take some work, but it's worth it. Have you been blogging for someone? Suggest more blog posts that could increase their traffic. Have you been working on software? Make suggestions of helpful additions to what you've already done. Get knowledgeable and get creative. Could they steal your ideas and go with another contractor? Sure. That's a risk you take. But chances are, if you've had a good rapport, they'll stick with you -- you are already trained, in place and ready to work.
Ask by suggesting your ideas over the phone or Skype. Conversation allows you an opportunity to answer questions about your suggestions -- if necessary -- and it reminds your employer you are pleasant to work with. It's too easy to skim an email and ignore it. Remember how a good journalist uses conversation to keep the interview going! Think of your working relationships like this: Conversations will keep them going.
Once a job is over, keep an eye on the company for a while. It's completely within the realm of professionalism for you to contact them one or two more times over the next several months with your ideas. After you've been told "no thanks" two or three times -- or if you notice they are using your ideas but not you -- then move along.
Tell us: Have you had success asking for more work? How did you go about it?