One of the things I've seen many novice authors do is attempt to hide what the novel is about for half the book or more. They appear to think that it adds to the suspense and mystery of the novel, but instead all it does is confuse and bore your reader. They want to know, at least on some level, what the novel is about within the first fifty pages at the very most (think more, the first five pages).
However, this doesn't mean that you have to spell everything out for your reader at the beginning. Please, no thesis statements at the beginning of your novel.
Instead, work to introduce the conflict early on, in some form so that your reader can get a handle on the story, or at least what the story needs to be about at the beginning. For example, say the main character is having problems with their mother and they get into a shouting match. This introduces the conflict (and will need backstory so we actually care about the characters), and also can lead us to wonder why this conflict is happening. As the story progresses and we learn more about the characters (and the reason why the main character hates their mother because their mother abandoned them at a young age to go become a cantina singer), the conflict can evolve as well.
Don't think of your story as a static beginning to end sort of thing. Instead look at it as an interconnected web of events that tie into each other in new and interesting ways. Develop it from the beginning of the story and throw the reader into the story as early as possible.
This is the main reason I don't like prologues for the most part. Either they're glorified infodumps, or they're windups (preambles) to the novel. The action doesn't start until the first chapter, which is where the book should start. The windup, prologue, or preamble should be for the author to allow them to settle into the story, but not for the reader.