The most important thing authors want to communicate with their readers is the main idea, which is the core topic that confirms or contradicts the title. Read the whole message, essay or book, before reaching conclusions. As in oral speech, when you must allow other parties to express their views thoroughly before you can reach a conclusion, you have to read every word in order to understand the author. When you must reply to the author -- such as in a letter -- you cannot afford misinterpretations.
Speakers can be angry, enthusiastic, pessimistic or indifferent, which give a different meaning to the message. Authors use words or punctuation to show emotion. Rarely will authors directly express their emotions, but you can understand them by paying attention to exclamation marks, which can show either enthusiasm or sarcasm, or rhetoric questions for issues that they think basic, but are not happening ("Can't I go on holidays with my kids?").
Always try to figure out the reason behind the author's message, particularly when responding to a letter. Experiences that motivated the author to write about a specific topic can prove crucial, especially when trying to decode a poem about a love affair, or a letter asking for salary raise. Do some background research on the author, in order to avoid misinterpretations and to respond accurately.
With the rise in popularity of instant messaging services and text messages sent by cell phone, written communication resembles more and more our verbal interactions. Read text messages aloud to get you an accurate view of the other party's tone. Pay attention to emoticons as well -- the artificial method to make face expressions.