Your own life is a valuable resource for writing material. Use experiences that shaped you or things you have seen that left an impression upon you. Pinpoint specific relationships you shared with other people or events that taught you something. These experiences are available foundations for subject ides for your writing. Love and friendship are common subjects because they are human experiences that authors experience in their personal lives.
Watch the news and take careful notes of specific events and issues in your society. The news is filled with popular subjects ideas for books including political novels, political intrigue or dystopian themes. Choose a few stories that you find interesting and expand on their ideas and themes to form a foundation for your own book. These stories are ideal for subjects ideas because social trends tend towards certain unifying ideas such as a general distrust of government or expectations of social status.
Become an active reader of subjects and genres in which you are interested. Understanding how other authors accept and adopt these genres provides you with a foundation for how you can do the same. They also provide you with the chance to choose which genre changes you accept and which you deny. Read critically and located the subject choices and changes that other authors make and ask yourself those same questions for your own novel. Through this you can understand popular subject ideas that already exist in literature and are already associated with your favorite genre.
Nature has inspired many authors throughout history. Simple observations of the wind, rivers or weather when compared to other observations about human nature can lead you to subject ideas with a strong naturalistic element. Modern literature includes urban environments as a new concept of nature. Connect the natural observations you find in nature or in the urban nature to your perceptions of human nature and see what subjects you can find. Emptiness in an urban environment opens subjects about human emptiness while emptiness in nature suggests subjects regarding refreshment and cleansing.