A month into a new year seems as good a time as any to discuss something very important to a story: the beginning. It is difficult to get invested in reading something if it cannot capture you from the very start. This may be unfair—I am sure there are plenty of really great novels out there which do not pick up until a few chapters in. However, when your partial manuscript is being judged on those first few chapters that is not a risk you can really take. You need to capture your audience from the first page, and then work to keep them interested for the remaining pages.
Introduce great characters in the first few pages. Even if the plot doesn’t pick up right away, it is easier to give the author the benefit of the doubt and keep reading if there are characters you feel connected to. [See the post a little while back on characters for more on this.] You can also draw a reader in by creating a setting that they won’t want to leave. It is easier to stick with a slower story if you feel like you can imagine being there. Also, just the overall style of writing can instill some confidence that the plot will follow.
That being said, it is still really important to make sure something happens in the first 20-30 pages. That long without plot development—even if it occurs within the middle of the book after the story has picked up—is too long! It is nice to have some kind of idea where the story is going from the initial chapters, even if you also include a synopsis which explains the future development. I want to be really drawn in from the first page, first sentence even. You only get so much time to capture your audience, so use it well!