1. Read the Framework for K-12 Science Education
The K-12 Framework for Science Education includes the directions for writing the Next Generation Science Standards. You wouldn't do the assignment without reading the directions, would you? At the very least, it is important the read the executive summary of the Framework BEFORE trying to understand NGSS.
2. Make the connection--K-12 Framework to Next Generation Science Standards
The next important step in understanding NGSS is to understand the connection between the Framework and NGSS and the process that was used to develop the Next Generation Science Standards. This will help to ensure that you understand the spirit of the standards and not just the words on the page.
3. Learn the structure of the Next Generation Science Standards
The Next Generation Science Standards (NGSS) are distinct from prior science standards in that they integrate three dimensions within each standard and have intentional connections across standards. Integrating these three dimensions has also led to a unique structure. Click the link above to figure out how to navigate through the standards.