Maintain a formal writing style. Write in the third person, and identify objects and samples specifically and quantitatively. Do not say "I scooped the green stuff into the flask" or "Danny helped to transfer the powdery main ingredient, don't think we messed up lol". Instead, "Five grams of green powder was transferred to the 500-mL flask."
Decide which chart or graph style best presents your results. Let's say you are measuring conductivity in response to temperature increase. Presenting results as percentage or fractional change of initial conductivity communicates temperature effect better than plotting raw conductivity values. In order to get quantitative verification that, for example, sample conductivity decreases as temperature goes up, a reader would have to convert conductivity measurements (ohm values) into percentage-change or fractional relation anyway.
Account for extent of error in your experimentation and the effect it had on the presented data. Make sure to mention determinate error--spills, sample contamination and other avoidable mistakes. Also, account for indeterminate error such as limited instrument precision. Substantial error can reduce data reliability--something to consider in discussions and future research recommendations.
Compare data with expected data from hypotheses. Note if observations support or negate relevant mainstream theory. This is a key portion of a lab report, since it is here that data interpretation is presented and analyzed.
Cite literature in support of accepted theory. If relevant or applicable, also cite research that goes against mainstream theory. Incorporate summaries of abstracts of these citations into discussion and data interpretation.
Reference literature that documents practical applications or ongoing real-world research of your subject. Advise on further research, with appropriate sources to add credibility to advice.