Cal Newport outlines the basics of how he reads when working on a project. According to Newport,
The key to my system is the pencil mark in the page corner. This allows me later to quickly leaf through a book and immediately identify the small but crucial subset of pages that contain passages that relate to whatever project I happen to be working on.
For the balance of Newport’s process, see his original post. For broader suggestions about effective and efficient reading, see for example Rick Ostrov’s Power Reading and James Sire’s How to Read Slowly.