Animals and People
Are you considering using animals or people in any way? Make absolutely, positively certain your project is acceptable. Many science fairs expressly forbid research involving animals or people because of ethical issues or even the risk of unintended harm (for example, taste testing peanut butters seems like a safe project, except that some people are deathly allergic to peanuts!). If your project is for a competition, keep in mind that human and animal projects will be scrutinized very closely. I'm not trying to discourage you from such projects (they are my favorite type, after all), but you need to be aware that real scientists adhere to strict regulations with regard to such projects. If you do perform an animal or human experiment, make sure to include a statement explaining the steps you have taken to ensure humane and ethical treatment of your subjects. This statement also needs to explain the reason why the animals or people are necessary to the project and why the project is worth performing in the first place. Get your justification in order before you are asked for it and include it in any reports or presentations that you make.
Controlled or Regulated Substances
If your project is at the college or university level, you may have access to controlled or regulated substances for your project. Make sure your rationale for using the substance is clearly defined and include a description of the safeguards in place to prevent misuse or theft of the substance.
Even if you aren't using animals, people, or a regulated material, you may well be working with a substance that requires special care or disposal. There are many ways that a substance can be hazardous. It could be flammable, reactive, toxic, radioactive, etc. Make certain that you collect Material Safety Data Sheets (MSDSs) for any chemicals used in your project and have them available with your report or presentation. Explain any special steps you are taking to ensure safe storage, use, and disposal of these substances. Make sure this information is available to accompany your report and presentation.
If you have an approved project and have collected all of the information you need to perform it safely, then you are ready to perform your study or experiment.