Whenever you are unsure about mathematical definitions/theorems/proofs/formalism, just refer to Elements of Mathematics by the Bourbaki group. (Yes, I'm a fanatical Bourbakist!)
If you are a heavy user of LaTeX:
Watch this lecture by Prof. Ryan O'Donnell for many useful tips that even an experienced LaTeX-er may not know
FiXme: the best package for annotation, especially when there are multiple collaborators