How should a freelancer know how the right tone in the proposal letters?

[Btaliat]

It is always important for the freelancers to learn more about how to sound whenever they writing proposals. They need to make sure that they don't sound too much informal, especially when the clients don't seem like that. You need to make sure that you are studying your clients mood for you to know how to sound whenever they are writing their proposal letters. What do you think should be the major factors that affect the tone of the proposal letters.