I’ve been asked this question twice recently – in a conversation on G+, and by a student at my Guardianmasterclass the other week. In both cases, the writers had encouraging feedback from agents, but one crucial criticism: the characters all seemed too similar.

And probably this wasn’t surprising because of their story scenarios. Both writers had a set of characters who belonged to a group. A bunch of flatmates, or a squad of marines, or a group of musical coal miners forming a choir. To outsiders, they probably looked identikit – they’d talk the same, use the same cultural references and have similar aims.

So how can you flesh them out as individuals?

1 Look for incompatibility

The first step is to assemble your cast carefully. In real life, if you were choosing a team, you’d go for compatibility and congruent aims. For a story, you need to…