Can any French typesetters (or of course English typesetters with extensive experience of French typesetting) give me the rules for which spaces should appear before and after the different punctuation marks?

I found this excerpt courtesy of Microsoft:

Note: When traditionally typesetting the French language a word space is inserted before or after several punctuation characters. These characters are colon, semi colon, question, exclamation, right guillemets, and left guillemets. Commonly the preferred word space used is a thin space of 1/8 the em. Some French typographers prefer to use a larger space character of 1/4 the em with the colon and some other punctuation characters. OpenType supports character substitution and language dependant variants.

but wanted to know if indeed it's a regular space (and also if it’s fixed space or variable) or whether different width spaces are used for different punctuation. I seem to recall reading a French site with the help of google translate which seem to indicate that different widths are used depending on the punctuation.

I'm about to typeset an important book in French (and next month the book will be in German so I will be back again asking questions :-) ), but for now I want to make sure I’m doing the French correctly.