There are several ways to reach a goal.
As for grammar field. You can read grammar textbooks but still be not be able to use correct grammar while you are speaking. I'm sure I have to reread all rules in which I don't feel myelf comfortable, but at the same time I need to be said about mistakes in my speeches and in blogs. I think I need it as much as possible. Sometimes it would be helpful to say me why it's better to say so-and-so. I've noticed that a lot of American teachers don't really feel comfortable to tell students about their mistakes. I guess, they try not to offend students. But that's why students keep doing mistakes all the time! We are here to learn. I'm sure, that the learning process needs that kinf of feed-back.
I know for sure that I also have to keep reading as much as possible and auditing, but I guess the second one should be less for those purposes. So, careful reading should help a lot.
I don't know how I can get the purpose to learn how to write requests about providing information if not ot be learned how to do it. I think I need some special knowledge about it. It can include knowledges how to address the letter, how to make sentances, how to finish it and mostly what is the best way of asking about it. Usually if you have no insiders at the company you would deal with public relations departments, so I need to know how to deal with them.
As for the third goal to know new words the reading is unlimited resource for it. I think, some quizes at school also might be very helpful for that purpose.