Jeeped has covered the techniques for displaying / hiding the non printing formatting marks.
Personally, I keep them on all the time, except maybe sometimes when I'm looking at final layout. I like to know what is causing strange spacing without having to take the extra "effort" to look at the underlying causes. But knowing the keyboard shortcut
is a good alternative because it allows you to turn them on and off quickly.
Another alternative is the tool I mention in my signature, "Crosseyes", I quite like it.
Formatting Problems? Install CrossEyes - http://www.levitjames.com/Products/CrossEyes.aspx****
This tool adds a pane that converts Word formatting into HTML/WordPefect like “codes”, displaying a WordPerfect like “Reveal Codes” pane. It is a great complement to MS’s inadequate attempt in the <SHF><F1> “Reveal
Formatting” pane.