At the interpreting assignment yesterday, my usual partner in crime was on vacation, so I had the pleasure of meeting a new colleague. She is just starting out, both as an interpreter and a translator, and of course was full of questions on how to find work and clients.
As expected, she asked for my “secret” after hearing that I had started freelancing not so terribly long ago myself, yet am having to turn down work, but as I have had to tell others before her, too, there is no such thing as “the” method or trick by which to find clients and jobs. I can only say what I do.
My “secret” is really simple: be visible. Get out there and network and spread the word about yourself and your services. How? Here is what I would recommend:

• Always have business cards with you to hand out at every opportunity – you never know when and where you may meet the next potential client. 
• Go to where your potential clients are, e.g. trade fairs.
• Get involved in your association, and make use of the local meetings and networks.
• Join online communities, both for translators and interpreters and general business networks. 
• Participate in forum discussions.
• Spruce up your website and update it regularly, e.g. with blog posts or a calendar showing your next assignments.
• Don’t forget to continuously learn, via workshops and seminars, and to talk about it, so people know that your skills and knowledge are up-to-date.
•  Go to live networking events, and above all not (only) those within the language industry, although those are important, too.

Something I read recently rings very true in this context:

It’s a human tendency to overestimate what we can do by ourselves and to underestimate what we can do as a group.

Especially in these times of ever greater and more extensive assignments, a reliable network of colleagues is key to not only being able to accept jobs you could never do by yourself, but also to your personal health and sanity – taking time off for yourself without having to worry about losing clients is only possible if you have a network of colleagues you can refer to without having to wonder whether the result will be up to (your) standard or whether they will “steal” your client.
I firmly believe that the times of the translator or interpreter as lone warrior are over. Our colleagues are not (only) our competition, but rather a valuable source of support, experience and knowledge. Just look at the numerous forums where you can ask for help on strange or unusual translations, ask about the reliability and solvency of a potential client or hear what others have done in a particular situation. We don’t have to do everything ourselves and repeat every mistake and learn everything anew for ourselves. By working together and sharing our knowledge we will not “give away trade secrets” or “hurt our business”. Ultimately we only benefit ourselves as a profession and as individuals.