When describing characters, you'll want to avoid focusing on the basic details too much. These may include hair color and eye color. I've seen many manuscripts that only described their characters' hair and eye colors. Avoid doing this. Instead, consider focusing more on the details that make your characters unique--the details that will make them memorable and stand out from the other characters in your book. Does your character have a tattoo? Do they have a visible birthmark? A scar? Bushy eyebrows? Piercings? Certain sense of style? Mention it! Little details like these will help bring your characters to life.

Young-adult (YA) books tend to focus more on descriptions, whereas books targeted toward adults tend to have less description, but that's not always the case. I personally enjoy YA books more because of those detailed descriptions. When reading books targeted toward the adult audience, I feel a little more disconnected than I do with the characters in YA novels.

A note on describing female characters: as a female reader, it can be incredibly frustrating reading books where the (usually male) author is describing their female characters. The instances where I get frustrated are when the author describes their male characters with traits like clothing style, personality, actions, etc., but when it comes time to describe the female characters, the only traits the author focuses on are the female's body shape, breast size, etc. Female characters are more than just objects to be desired, so please describe them with respect. Thank you.