Here are some helpful links:

Avoiding Plagiarism

The MIT handbook on academic integrity.

Scientific Writing

"The Science of Scientific Writing" by George D. Gopen and Judith A. Swan (PDF)

"Errors in Mathematical Writing" by Keith Conrad (PDF)

"A Guide to Writing Mathematics" by Kevin P. Lee (PDF)

LaTeX

The Cambridge University LaTeX Page

"A Short Math Guide for LaTeX" by Michael Downes (PDF)

"The Not So Short Introduction to LaTeX 2e" by Tobias Oetiker (PDF)