When one wants to write a letter to the Rebbe, be it a bakasha for a bracha, a Pan (pidyan nefesh typically written on Erev R"H or your birthday) or a Duch (din vecheshbon, writing to the Rebbe about your achievements in a certain period or area) a chossid would prepare himself properly and take the moment very seriously. There are many preps that different people do, it's based your own hergeshim and discussions with your own mashpia. After writing the letter, randomly select a volume of Igros (or any other Sefer of the Rebbe's Torah, Igros has become the norm now since it is the most practical way to get a clear answer) and insert your letter into a random page. Afterwards, sit down and learn the letter and see what the Rebbe is discussing, and most of the time you should discuss the letter with your mashpia, you shouldn't rely on your own deductions.
I should add (although this should be obvious), you must take this serious to work, I know people who like to disprove it based on their own experiences, they were critical of it from the beginning and wrote a letter with the intention of discrediting this whole thing, and lo and behold then letter he opened up to had nothing to do with him...
on another note, one of the most amazing stories I heard first hand from the person assisting the writer, this person guided the writer through the process and told him to go over to the bookshelf and select a volume and put the letter in, afterwards he brought the sefer over and they began to look at the letter and they noticed it was the Frierdiker Rebbe's Igros, not the Rebbe's, they nonetheless learned the letter and the FR was addressing his exact issue, he had his answer. but afterwards, he was upset he used the FR's Igros and not the Rebbe's so he decided he's going to stick the same letter into the Rebbe's Igros, the Rebbe's letter he opened up read "I'm surprised you ask me this, being that the Rebbe the shver already answered you on this matter"
