The first rule of world-building is available physics, which basically means that if you want it to feel real, it has to follow the same rules as this world, from gravity to how human behaviour works. If you have a fantasy element that doesnt obey the laws of physics, make sure that it has a fantasy explanation.
Trudi CanavanSo what were you [Sonea] and Dorrien discussing before?' Akkarin asked. She turned to regard him. 'Discussing?' 'Outside the farmhouse when I was buying the food.' 'Oh. Then. Nothing.' He smiled and nodded. 'Nothing. Amazing subject, that one. Produces such fascinating reactions in people.
Trudi Canavan