I recommend you just start writing as if you were writing a plain text email. Then come back here and see you how can apply some formatting. Best way really is to learn by doing (running pd2tex a million times in the process). Trying to learn the system before you start writing will just lead to frustration. About the only important thing you should remember up front is
Paragraph break is created by putting an empty line between paragraphs, i.e. single newline will not break paragraph - you need two.