Finding bugs in latex documents that will not compile

When you try to compile a latex document that contains an error - the compilation will halt with an (often cryptic) error message and a ? prompt. At this point, you can jump right to the line containing the error in your document by simply entering edit at the prompt i.e.

? edit

This launches vi and takes you straight there! When you're done, just save and exit and try compiling again. Repeat if necessary.