Pauline Rowson explains how she develops the characters in her crime novels

Creating a likeable, interesting and complex main character, one the reader can have empathy with, one they want to trust, feel his/her pain and disappointments, root for throughout the story is vitally important and it's not just the main character but the supporting cast, the villains and the walk-on parts who all need characteristics that are believable even if they are eccentric. The cast must be real to the writer and therefore real to the reader.

I develop my characters using spider grams.  I draw a circle and put each character in the centre of that circle and then I throw out lines and ask a series of ‘open’ questions about each of them. 
For example, if I have the victim in the circle then I’d ask questions such as who is he? How did he get where he is?  Why would someone want to kill him?  Who killed him? How was he killed? What’s his background, family, education, experience? What’s his occupation? How old is he? Where does he live? What’s his personality? What does he look like?  What has shaped him? How are the victim’s family, friends and others going to react?  How do they see this character?  What’s my main character (in my case my detective, DI Andy Horton) going to do next?

I draw up character profiles for each of the main and secondary characters, some might be sketchier than others.  But that doesn’t matter because it isn’t until you start putting dialogue into their mouths and have them walking around and interacting with people that they come alive.  Until then they are just notes on a piece of paper. But those notes can be added to as your characters start to take shape through your writing. 

The characters’ actions drive the plot. The surprises, twists and turns all spring from the characters' motivations and as you write you will find ideas occurring to you that you hadn’t previously considered.  You might also discover that someone you thought was going to be a minor character turns out to be much more interesting when you write their part, and a major character becomes boring and sometimes unnecessary, if that happens then cut him out.  

As you write ask yourself what will this character do in this situation?  What will he/she do next? Throw out more lines around that spider gram. Continually ask questions about each character. Answer them as the novel progresses. Shape and reshape them. Put them in difficult or unusual situations, and as you do the story will unfold and the tension will build.

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