One of the more serious mistakes that I see new writers make is what I call ‘Delayed Character Description.’
If the writer does not specify how a character looks, dresses and talks early in the piece, then the reader will release their own imagination and begin to formulate a picture in their minds. I’d opine that this image formulates quickly, as most people like to attach a face and body to a character.
Now, it may be that it’s not important what your character looks like, but if you want to control this aspect, I would advice you to do it early on in the work.
Personally, I find it disconcerting when no physical description is given and probably would not read very far into the work. Even worse than no description is the delayed description.
Call it a dream disturbance that you do not want to happen. To related that to real life: Imagine that you’re talking to someone and all of a sudden they morph into another person. Imagine that you’re flirting with a cutie, leaning hard on them and wondering if you’re being too aggressive, and suddenly their dentures drop out or they revert to a prepubescent state. Would that be enough to make you forget what you were talking about???
Delayed Character Description can be just that jolting. Don’t put a bag over the reader’s head and expect them to listen to dialogue; don’t expect them to stand in the kitchen and listen to what’s going on in the bedroom. Human beings are visual creatures; they want to SEE most of all.
Author’s Note: This rule goes double for location. Don’t allow them to imagine that they’re in Europe and find out several pages in that they’re actually in South America.