Decide where the kingdom is situated geographically. A kingdom located in the mountains is different from a city located in the desert in terms of what the architecture looks like and who comes to the city.
Determine who is running the city. A kingdom is run by a monarch, but other people may be controlling the monarch. Decide how the people in charge feel about magic and how that affects the lives of everyone who has to live with their rules.
Create the magic system in your kingdom. Decide if magic is something that everyone can use or if only a few people can use it. This affects the way people treat magic and regard it. Consider what magic can do and what role it plays in the kingdom.
Think about who lives in the kingdom. Is the kingdom highly stratified with nobles at the top and serfs at the bottom, or are things more equal? Think about if there is a way for people to move from one level of the kingdom to another and how that affects their dreams and ambitions.
Decide what the kingdom is proud of. The things that are considered a kingdom's pride affect the way the kingdom looks and feels. For example, a kingdom that is proud of its ability to conquer puts a great deal of effort into waging war, while a kingdom interested in the arts has a strong interest in artists and writers.
Determine what role magic plays in the kingdom. Magic might be something only possessed by the elite, or it might be something that is meant to be hidden. A kingdom that uses magic as a common resource is different from one that wants to ban it.