Basically, a character worksheet is designed to help an author get to know the characters within their story in order to make the character read more life-like. If done right, the worksheet answers various questions about the personality and backstory of the principal and secondary characters, sort of like a questionnaire from a dating website. A good worksheet will also have the author asking questions about characters’ motivations, intentions, weaknesses, strengths, and quirks in light of the plot, but will contain large quantities of information that may not make it into the final product.
For my WIP, I started with a basic description of each member of my MC’s family, as my plot hinges around familial relationships. Then I added a couple of important minor characters, including a best friend and a villain. These descriptions started much the way real life introductions do, with the physical observations of hair/eye color, height, build, etc. and moved into personality types. Using prompts from Mary Cole’s WritingIrresistible Kidlit: The Ultimate Guide to Crafting Fiction for Young Adult and Middle Grade Readers, I came up with each character’s main objective (a great way to look for tension-building conflicts), strengths, weaknesses, and general outlook. I highly recommend Cole's prompts (and the entire book!) as she is very thorough.
In the process of doing all this reflection on who these people are, I found what I learned about my characters had an impact on the plot, of which I had made a very rough sketch prior to thinking much about the characters. As I made decisions about the characters, the plot filled itself in (and slightly changed). Initially I knew I was writing a story about a tween wallflower who struggles with the shame of an alcoholic father going through a stint in work-release jail. When I filled out my worksheets, I realized I wanted to add more dimension to the story by introducing a villain, who comes on the scene during the dad’s absence. By thinking about what makes each of the players in my story unique, I realized where certain characters could make the story sparkle more using information from my worksheets. Studying their characteristics and how they interact with my protagonist also has helped me in trying to keep my plot focused, and made it easier for me to decide how to use each character in furthering the plot. And there is always the huge concept of voice. By acquainting myself with my protagonist in the earliest stages of writing, I have found expressing who she is so much easier than in my previous works, where I focused on writing a plot-driven first draft and trying to add character depth in revisions.
Obviously, this topic could fill a book in itself, but here are a couple of character worksheets on the web if you want a quick start.
http://jodyhedlund.blogspot.com/p/character-worksheet.html: covers the essentials wellhttp://www.epiguide.com/ep101/writing/charchart.html: more detailed
Please use the comments section to add your own recommendations!