Scientists and engineers rely on authoritative sources of information they can trust. Be a good information consumer -- evaluate your sources. Look for sources that:
A trustworthy sources doesn't have to meet all of these criteria, but it should meet at least some of them.
Evaluating Information -- More on how to identify authoritative and trustworthy sources.
Image -- Researches looking at data, Colorado School of Mines
You should focus on using authoritative sources, but you can use both authoritative and popular sources for your project. Take extra care evaluating (and think twice about using) sources that:
What About...
AI? Artificial Intelligence (AI) is increasingly being used to identify publications and other information for scholars and researchers. Check with your advisor and the Colorado Science and Engineering Fair's Student Researcher Information on the use of AI for your science project. Remember: You as a scientist or engineer are responsible for verifying citations and other information retrieved using AI.
Wikipedia? Wikipedia is a good starting point -- but remember, it shouldn't be the only source of your research. Wikipedia has a wide range of contributors that write articles, from authoritative and scholarly to weird or unreliable. Use the criteria above to evaluate a Wikipedia article -- focus particularly on, "Does the article cite its sources?" "Do those cited sources look authoritative and trustworthy?"
YouTube? YouTube excels in demonstrations, "how to", and experiments. Again, use the criteria above to evaluate a YouTube clip.