Many professional editors have a column guide. For example, below you see in the Powershell editor a veritcal line at column 80.

This marker comes in handy, if you want to print your files. In Emacs I usually check for the column 80 in the status line.

However, I usually forget to check, and when I print out stuff or publish, I got line breaks where I don’t want them. Passing the 80th column for comments is not a problem, as a simple Ctrl-q forces Emacs to break the lines nicely and add comment symbols at the beginning.

But after hitting Ctrl-q, Emacs produces this:

There is, however, a package, that mimics column guide seen in other editors. The package is called “fill-column-indicator”. Installing this package will do the trick. After installing, you only have to add the following lines to your .emacs file:

I added two hooks, so the column rule appears automatically in Gams and ess.

More information can be found here: http://www.emacswiki.org/emacs/FillColumnIndicator