If you are new to light novels in general, you should know that they are often serialized. This means the story might develop over multiple volumes. So be prepared for cliffhangers at the end of some volumes. And Maou Gakuin might also have some in - jokes or references specific to the Japanese culture or the light novel community, so it could be helpful to do a bit of research on that if you're not familiar with it.
You should be aware of the character lineup. There are likely to be a main protagonist and a host of supporting characters with their own unique personalities and abilities. Understanding these characters can enhance your reading experience. Also, light novels sometimes have their own unique world - building, and Maou Gakuin is no exception. Familiarize yourself with the setting, like the magic system, the political structure of the world in the story, etc.