Having a translation proposal template will save you work in the long run, but you still have to understand and know the prospective client. Translation services are needed by a variety of private sector businesses and public sector clients, including medical offices, government agencies, law practises, insurance and financial firms, and more.
That means gaining some understanding of their sector, business, the work they do, and their clients or customers. If you have a specialty, like working for government agencies, look for clients that fit in your niche, so that experience can be part of your proposal