Don't comment their code. If it was hard to write, it should be hard to understand and even harder to modify. Don't pollute their code with documentation, variable dictionaries, structure and other such impurities. Documentation is for simpletons who can't read listings or the object code from the dump. Don't draw flowcharts.
Flowcharts are, after all, the illiterate's form of documentation.
Don't read manuals. Reliance on a reference is a hallmark of the novice and the coward. Don't use Cobol. Cobol is for wimpy applications programmers. Don't use Fortran.