Grid systems are one of the most useful tools in graphic design. They can range from a simple baseline grid and margins to a complicated modular system. Some examples:
I'm interested in how to decide on a grid system to use.
Do I need 3 columns, 7 columns, 12 columns, how do I know?
The baseline grid obviously has to relate to the font sizes used, so do I choose font sizes first then work out a baseline from there and work out margins, gutters and columns from that, or do I work out font sizes and baseline from the grid?
Where do I start?
Note: I'm specifically interested in print design. Grids in web design have a lot more technical limitations so lets stick to print.