5 things about worldbuilding
1. Every story requires some worldbuilding to a certain degree. Obviously something set in current day Britain won't require quite the same level of worldbuilding as a fantasy novel, but don't assume that because you're not writing fantasy or SF, you're not worldbuilding. That cute cafe you invented? Worldbuilding.
2. If you've started with a character, ask yourself what sort of environment would create an organism like this. If you start with an environment, ask yourself what sort of organism would evolve in it. What would you need to be able to survive there? Darwin's theory of evolution is a very useful tool when trying to figure these things out. Think about how your characters live, how they structure their society, how they're born, how they die.
3. You don't have to know every single detail about your world before you start writing, so don't be afraid to start that first chapter before you've worked it all out. Sometimes the way to figure things out is to put your characters into your new world and see what happens. It helps to keep a record as you go so that you can remember the name of that innkeeper who turned up in chapter seven when he reappears in chapter twenty-three.
4. When you're in the head of a character, think about how they perceive the world around them, and try to reflect that in their inner voice. We might describe something as being 'white as snow,' but that's not going to happen on a burning hot planet like Sittan where snow doesn't exist.
5. Our world is full of incredible plants, animals and physical phenomenon and all of it can provide inspiration for your imaginary world. A newly discovered animal or strange bacteria can be a building block for your own creation. When building the world of the Second Species, I borrowed from all over the place - mole rats, slime mould and ants with a toxic bite all provided grist for the mill.