There are many aspects to writing a novel that one has to keep in mind. One that rather obvious, but can be easy to forget about, is the simple concept of time. While you may inherently know where you are in the timeline of the story, are you sure the audience does?
A very common approach to writing a novel is to use a variety of storylines. You might have two or three that inevitably lead to a result that either creates a global ending or contributes to it in one way or another. The evil character might be weakened in the final climatic scene and one of your storylines can be about how that comes to be while another storyline gets your hero to the proverbial finishing line and so on.
The multiple storyline approach is a time tested one. That being said, it also introduces subtle problems. Switching between storylines can result in problems of time. While writing them, you may just assume that the storylines are taking place at the same time, but how does your reader know this? If the individual stories are taking place at different times, have you alerted your reader? If not, the story can quickly become an incoherent mess.
You need to use transition cues to avoid time problems. These cues are phrases or words that let the reader know you are making a transition to another time or storyline. You can make them witty, subtle or blatantly obvious. It doesn