Character descriptions can be tricky. You want to give readers some clues about what characters look like without going overboard.
As each character enters a scene, provide a brief description of that character’s physical appearance. As with setting descriptions, keep these brief and somehow related to the action and always in the point-of-view character’s perspective. What does the heroine notice about the hero when she sees him for the first time? What does she notice about him after she’s spent some time with him? Don’t just tell the reader what he looks like. Show him doing something related to his appearance. And reveal how his appearance affects her.
For example, rather than writing, “John was tall, with black hair and brown eyes, and he wore a hat,” try something like this: “John ducked slightly as he entered the room. When he saw Mary standing in the corner, he removed his Seattle Mariners cap, revealing a mop of thick black hair that stuck out in every direction. His dark eyes darted back and forth as if he expected a wildcat to lunge at him. Mary stared at the thick fingers of his left hand as they squeezed the cap. He wasn’t wearing a ring.” Here you’ve shown that John is tall, with black hair and brown eyes. But you’ve shown the details within the action of the story rather than simply telling the reader the facts.
Vary your descriptions. Don’t show each character’s clothing every time he or she enters a scene … unless your main character is a fashion designer or has some other reason for noticing people’s clothes.
Showing the appearance of your point-of-view character can be tricky. Since she can’t see herself, it’s more difficult to show what she looks like. Using a mirror sometimes works, but this method can appear contrived, especially if she doesn’t have a good reason to be looking in a mirror and if you don’t show what she thinks about her appearance.