Get to know other translators, by meeting them at local meetings of translators, by going to conferences like the annual ATA Conference, by talking to other translators on-line in places like the Foreign Language Forum on CompuServe, or by tracking them down through friends. Find out from them who is doing what in the industry and then use that information to develop your marketing strategy. You want to target agencies which are most likely to use you. You also want to be known in the profession, so that if someone is putting together a team of translators for a large project, your name gets mentioned. Get to know agencies and the people who work there using the same techniques that you use to find translators.
Agencies appreciate professionals who are involved in the industry and committed to translation.
And, the more agencies which know you personally, the more likely you'll be remembered when they are trying to figure out whom to give an assignment to. Eventually a translation will come your way. Sooner or later, the agencies will stop passing over your name in favor of someone else and will call you. Know what you want to charge for your services and what services you can provide, including what material you can translate and how many words you can do per day. Recognize that you will have to negotiate for the job, although many agencies offer work using a take it or leave it' approach.