Write your name, the date and the names of other lab partners at the beginning of each entry. Also indicate the time at which you performed that experiment on that particular day. You should record the date of the experiment at the top of every page of your entry.
You should record all of your raw data. Any calculations you make, you should write in the notebook. Do not calculate any mathematical operations in your head. Write them down in your notebook, so that someone investigating or attempting to do the experiment can know all of the calculations and algorithms you used to arrive at your answer.
Write the purpose of your experiment. According to the Xavier University of Louisiana website, it is important to avoid the language of learning and to use that of science. For example, do not write as an objective anything beginning with "to learn." As the website states, learning objectives have no place in the lab notebook of a professional scientist. A more appropriate scientific objective would begin with a phrase such as "to identify" or "to evaluate."
This section should be brief and concise. You should describe the methods you will use to complete your work on the experiment that is the subject of the entry. This part of your report should be no more than a page in length. Attribute all sources you have used to generate the ideas for the procedure you are using. Provide a bibliography. Follow the American Psychological Association style that most of scientific disciplines use.
You should record any data you acquire during the course of your experiment, whether it is mass, volume, length, etc. Use exact figures: do not round up to the next multiple of 10. For example, if you are doing an experiment with soda and its reaction to an acid tablet in which you must record the height of the explosion resulting from the carbonation, if you measure 3.9 feet, you cannot write that as 4 feet. It is a breach of scientific ethics to do that.