The American expat Amerloque has a great overview of the French election procedure itself, including "les professions de foi", mailed to every voter before election day to describe candidates' positions, and the voting booth, which includes "a somewhat stentorian voice" that rings "A voté."
No candidate here in France can ever really say that the voters 'didn't know' about her or his message: all registered voters receive this package of professions de foi and it is simply up to them to become as informed as they desire. The French voter who genuinely wants information about the candidates and their platforms will take the necessary time to read and attempt to understand these professions. From Amerloque's experience, the information contained therein frequently contributes to animated discussions at the office: some candidates' words, phrases and positions can be examined and parsed in detail over several days – especially when they are at variance (sometimes significantly so !) with versions appearing in the media.
Amerloque also adds a 13 point list covering all the reasons a vote can be invalidated, including the obvious:
13. Envelopes containing no voting slip whatsoever are null and void.
And the downright odd:
11. The voting slip contains written insults of candidates or of other.