Great resource here: http://www.thegridsystem.org/

Remember to break it so it retains it power.

Here is a preachy little quote from the site,

“The grid system is an aid, not a guarantee.
It permits a number of possible uses and each
designer can look for a solution appropriate to his
personal style. But one must learn how to use the
grid; it is an art that requires practice. ” - Josef Müller-Brockmann