We see them in our minds. So clear and precise. But, how do we show them to our readers if we are not completely familiar with them?
What does your character like for breakfast?
What is his or her favorite color?
So many questions we never think to ask ourselves. That is why I often refer to this checklist I came across. It's enclosed as an an attachment in pdf. format to be read with Adobe Acrobat Reader. I hope it helps.