General guidelines include (but are not restricted to) the following:
1) Quote only the relevant part of the message you are answering to
2) Subject lines should be clear and indicate the language(s) involved (i.e., with the notation Eng > Ger or Ger > Eng) and the subject query (e.g., Ger > Eng Bezugsperson).
3) Answering to a query, don't change the subject line.
4) Add always as much context as possible (entire paragraphs).
5) Describe the kind of text you are translating the the special field it belongs to.