character bios
I have several problems with character bios.
1. I very seldom see realistic characters created using character bios. Far too often such characters are too big, too strong, too handsome, too smart, too educated, etc.
2. Even when the above problems are solved, such characters usually read like they aren't characters at all, but Frankenstein's monsters, pieced together creations made from the parts of dozens of real people, and the seams always show.
3. The writer always, always, always seems to put in far too many details about such characters. More than the reader needs to know, and more than the writer should know. I've heard variations of the grade school line often, and I just don't believe it for a second.
4. This is a major problem. The moment you do a character bio, you've changed the story. Now the story will be written according to the character's traits, knowledge, abilities, etc. It's unavoidable, in my opinion. This isn't how real life works, and I don't think it's how good fiction works. In real life, people are forced to adjust to the situation. With character bios, the situation adjusts to the character.
There are certainly writers who can pull off character bios really well, but these people are seldom beginning writers. It's a tough, tough thing to do, but it's one of those things, like outlining, that appears to make things easier for new writers, when in reality it makes them harder.