Make it easy for a girl to answer your letter. Ask her questions.

Make it easy for her to answer you. In the end of your letter ask her a question. If she decides to write you back – she won’t have to think hard what to tell you. You already asked. There are two types of questions you can ask in the first letter: general and specific. General questions are like these:
what is your favorite club?
What flowers do you like? Etc. (flowers are always good – she may think you want to buy her some).
Read her profile and look at her pictures carefully and then ask her specific questions.
What ocean is behind you on the picture?
How did you get on that tree? Etc.
Overall rule: be friendly. Don’t ask a girl:
What did you do to gain all that weight?