One thing I wish my teachers understood about me is that I dont like to socialize. For example, if we dont get to pick partners, and the teacher decides to put me with someone random, I wont be to confirmable talking to them. But if the students get to pick partners and I decide to go with someone I already know, I'm going to be way more confirmable, then doing it with someone I don't know.
Informal letters can be made more conversational by using contractions, calling the recipient by name, and telling the recipient any news of his friends.