Everyone has a different preference for seeing the characters. Some like when they're described, because it's easier for them to keep a consistent picture, particularly young children. Others, however, dislike it, and want to form their own pictures. I've been told a few times that describing the characters takes readers out of the story and to let the readers use their minds' eyes to fill in the blanks unless the description is important to the plot. One time someone read an old sample of my work and said, "I don't need to know that hair-color of every single character." When I told him that I only do it to tie it in with something, he said "That has to be hardly ever." I've also read on websites to "keep descriptions to a minimum." The author said that he or she is against the author of the book describing the characters to the reader, and that the reader should picture everything, except for something that's important to the plot, like an eye that has special effects. Then he or she said, "Other than that, who cares if the character has blonde hair, blue eyes, etc?" But why should that be such a big deal?
Look at the
Harry Potter series: most characters are described in more detail than in any other book. Anyone who's read the books know most of the character's hair descriptions, and what they wore to formal occasions. Yes, some descriptions are crucial to the plot, such as the scar on Harry's forehead, his green eyes from his mother, his skinny body, and Dudley's heavy body. But the fact that Hermione had bushy brown hair, Luna had waist-length, scraggly, dirty blonde hair, Dumbledore had a long white beard and half-moon spectacles, or even the fact that Tonks had short, spiky hair that changed colors, were not so important to the plot. However, they were important to their characterizations. If the idea of only describing what was essential to the plot and nothing else, and leaving the readers to picture the rest was that important,
Harry Potter wouldn't have been so popular. There would definitely be no
Harry Potter theme park, no
Harry Potter products, no
Harry Potter movies, maybe even no
Harry Potter books after the first one. The first book would've received many horrible reviews about J.K. Rowling being a "control freak." People would've complained that they didn't need to know that Harry had black hair, Ron had red hair, and everything else described that wasn't important. If that had happened, J.K. Rowling would probably still be as poor as she was when writing the first book, maybe a little wealthier, but unlikely even working class.
Most authors do believe in keeping their descriptions to a minimum and letting the reader picture about everything. I, however, tend to be a control freak. I like to describe my characters in lots of detail, and want my readers to picture them that way. However, I do leave some characters to not be described, or certain parts of their bodies to be pictured by the readers' imaginations. For example, one my characters is just described as "bald." The readers can picture everything else about that character. But my protagonist is described in lots of detail. I describe her hair as, "pale blonde, straight, and tailbone-length." I also say that she has narrow shoulders, blue eyes, her height, and what she's wearing (with two descriptive words at most). I'd suggest, though, that if you're planning to publish a book with detailed descriptions,
do not info-dump. That only bores the reader. Instead, describe as you go along, and try to describe only when a certain situation ties into it. When I described my MC's body structure, I tied it in with a painful situation, where felt that narrow shoulders weren't the best for whatever the situation was (I don't want to spoil it).
So there are two sides of describing your characters. It's really up to you to decide what you like, and what your intended audience might like. If you're into not describing, so that the readers can picture the characters their ways, that's fine. If you're into being detailed with your descriptions, like me, that's cool too. But remember to let the reader picture
some things.