It is important to cite the sources of your research. You must give credit for others' ideas, data, and words.
There is no single citation style for engineering. If you're unsure which to use, I recommend asking your advisor or professor.
If you're preparing a manuscript for submission to a specific journal, consult the journal's guidelines for formatting and style.
TIP: EndNote software can do much of the work for you. See this page for details.
ACM: Association of Computing Machinery
ASCE: American Society for Civil Engineers
ASME: American Society of Mechanical Engineers
For citation styles for related science disciplines, see this page.