Make your notebook as efficient and accurate as possible. Some more common tips include:
*Use permanent ink.
*Initial and date every page.
*Leave a blank page or two in the beginning for a Table of Contents.
*Draw only a single line through all errors.
*Create a table of chemicals & relevant properties with each experiment.
*Record what you have done.
*Record all observations and explanations of why they happened.
*Be descriptive with titles & headings.
*Start a new page for each experiment.
*At the end of each lab, ask yourself, "Can I recreate this experiment/my results with what I have written down?"
Adapted from "Organizing your lab notebook"
To find the CAS number of a molecule look it up in the CRC Handbook of Chemistry and Physics: