I learned that paragraphs should be indented with a tab set at five spaces. I'd say that conventions are not universal, so please yourself, to the extent that tools and bosses allow. I follow conventions that make sense to me, or that I haven't thought about, skip those that don't.
I think one should be consistent in the proper context. When I lived in Germany I slowly became aware of how different their typewriting conventions were from ours. They would double space letters to indicate emphasis, whereas we would underline a word or phrase. Then there's the whole punctuation inside or outside of the quotation marks (or whatever punctuation is used to indicate reported speech). Having worked as a writer for over twenty years, I am happy to follow the written conventions of those who pay me at the end of the week. Another great convention is whether to use a serial (aka Oxford) comma in lists of three or more words or phrases. People really seem to get bent out of shape on that one. The humorous thing, to me, is that these orthographic conventions are pretty much arbitrary and historical in nature, but we all like to think that something we've been doing for years has purpose and meaning, and that the language would suffer without it.
