Before the chemistry lab begins, write down everything you will need to perform the upcoming lab experiment. This will allow you to leave your textbook at home, providing you with more lab space. Even if you are not sure you will need a piece of information, write it down anyway just to be sure. Drawing pictures of reactions and lab instrument set-ups can also be helpful. An important thing to write in the lab notebook is any considerations or warnings about the chemicals you will use in the upcoming experiment.
Write in the lab notebook during and after your experiment with enough detail so someone else could take the notebook and repeat the experiment if necessary. This serves as a record of what happened throughout the experiment, so if you find miscalculations or errors later on, you can go back to the lab notebook and find out how these errors may have affected the results. This also helps you understand what you did in the experiment even after a couple months have passed.
Write down any calculations you need to do before, during and after the experiment. Always write out the full equation in the lab notebook the first time you use it, so if someone needs to figure out how to do the calculations or if you need to go back to the original formula, it is written down for you to find. This also makes things easier for those who need a formula or calculation refresher a couple weeks or months after performing the initial calculation.