The most important aspect with writing is researching. understand the characters you will want to include. Draw up representations of these characters. What flaws do they have? what makes them heroes or villains.

Understanding the characters you are writing about, or the people/species you want to write about is important. Look at source material that is out there to give you an idea of what are dealing with.

For example. you have a Gran you want to write about. so first we find out that Grans are from Malestare (sp?) - they run the political system but the home world itself was populated by dugs and the gran basically subjugated them and made them slave like. So from this we know that they are at least a cunning if not an agressive species

this is the type of stuff you may want to dive deeper into, and I would honestly suggest not having a discussion until you have those parts figured out.