There are a good number of options. The first (once again) is to take a look at other authors who have already released books in German. Who translated their books? Were those authors satisfied with their translators’ work? If so, you could write to those translators to ask if they might be available for your book. That said, a personal reference remains the best approach.
Another option is to search on the web for translators who work for indie authors. There are some out there, and their websites usually include references.
Beyond this, you can also look at the membership list of translator associations for translators working in the language combination you are looking for. For more about how to do this, see section 6.3.
Independent translator or agency?
Some authors assume that working with an independent freelance translator will be more complicated than working with an agency. But that is by no means always the case. Freelancers can also work in teams and deliver edited, corrected and completed files, potentially even in publication-ready format. Of course, agencies also provide certain advantages, for example if you need to have your book translated into several languages simultaneously, or if you are shooting for a publication deadline that is coming up fast and don’t mind that given the circumstances, the agency will probably split the work on the series (or even the book) between multiple translators.
There is, however, a lot to be said for having a single translator work on all your books. Just as each author has their own distinctive voice, your translator must also find a voice for your novel that reflects your style. Together, you both define what will be your German voice, and that voice should come through in all your books in German. Using the same translator all the time also has the advantage that she will already know all your work and so can guarantee a certain stylistic continuity. This also creates a personal rapport between author and translator that is the basis for true teamwork. You know each other and you trust each other. You’ll find this to be extremely important: with every book you’ll feel as though you are entrusting your translator with your “baby.” Naturally, knowing exactly who is looking after your children is a tremendous relief to any “parent”.
From: “Selling your novel in Germany”