The Too Much Information Technique sometimes can be used for comedic value. But it is what it is--completely unnecessary. Writers can get caught in the TMI trap because they feel the need to explain certain things in minute detail, like the following: character appearances, personalities, backstory, settings, and emotions. Writers may try to pack as much information in one paragraph to two paragraphs, or they constantly mention the same information throughout a story.
Character Appearances
First chapters are most vulnerable to TMI, because that is when the main characters are introduced. One way is through the Diary Correspondence, in which the story is in first-person perspective.
Example: Japanese but a quarter Irish, Tawny's mixed heritage gave her the pretty, gorgeous looks that girls get jealous over. Her long, dark hair always smells amazing, so I steal her shampoo sometimes. Because of her Irish ancestry, her eyes are a lighter brown than most Asian eyes, and make her look like Anne Hathaway. Her lips have a perfect cupid's bow and her nose is cute and round. She's only five foot two so she's made fun of because she's short and a size zero, but at least her legs are longer than her torso so she's really photogenic and she never has to worry about having a muffin top.
Even though I am her BFF, I am her complete opposite in every single way imaginable. I have cropped pixie hair. I'm half Mexican, Cambodian from my grandfather's side, and Canadian from everyone else. Tawny wishes she had my eyes, because mine are smaller but more half-moon-shaped. My lips are thin and pinkish and my cheekbones are pretty average, so I don't stick out in a crowd. Well, unless you count the nose piercing, but people don't usually see that from a distance so whatever.
Pant size? Proportions? Celebrity reference? When a character seems to pay obsessive attention to detail while being broadcasted as normal, something is wrong.
You may feel that telling the audience right off the bat exactly what your cast looks like is better because then they have something to refer to later and you don't have to mention it again. But doing so actually takes the focus away from your story, slows it down when it should be giving its most attention-grabbing performance. In the example, there are many interesting things about the characters that the reader didn't know. But they're distracting. They don't move a plot forward and they don't make your character any easier to relate to than another described in less words.
How to fix it: There is nothing wrong with letting the audience know what your character looks like. But it's best to keep descriptions about appearance short, spaced out, and relevant to the story. By spaced out, I mean that descriptions should be constructed throughout a chapter, not just one paragraph. This helps reader focus on what should capture their interest more: the character's actions. Secondly, find ways to weave information about looks when it's relevant. If there is no reason in the story to disclose the color of a character's belt, leave it out.
Character Personalities and Background InformationAgain, first-person perspectives are prone to giving TMI about a character by excessively making the character talk about himself or needlessly reiterating his main personality traits. Case in point: Diary Correspondence, Chapter 1.
Let's say the protagonist is in college, but isn't a very serious student. TMI would occur when he explains his study habits before the author makes him demonstrate it. Readers know how to infer. You don't have to give them a character sheet before the action starts. Your story is not a dating site.
Sometimes, the author includes a trait that is insignificant to any decision or plot point in the story. Generally, this resembles a dating site form: hobbies, likes, dislikes, favorite color. This should not be confused with Intentional Randomness, because at least that has a comedic purpose to it.
How to fix it: Show, don't tell. Have the character demonstrate his/her qualities through the plot and interaction with others. If it's background information, make sure there's a good reason for including it. The cast can be your mouth-piece; just don't make the character speak for himself as if he is being interviewed for a job.
Granted, there needs to be a balance. It is up to the writer to judge whether or not something needs to be fleshed out or briefly mentioned.
Part 2: Settings and Emotions