creating a grid

i want to create a grid for one of my designz, i want it to look like graph paper grids. how would i go about doing this?

Gainz...

this is what i do:
(but i'm not exactly a guru @ graphic programs)
fill white
then filter > texture > patchwork
adjust the size to your liking and obviously
make that other option to 0, i don't remmeber
what it was called...

Draw them, or make a pattern...

expanding on what paavo said..

create a new document that is for example... 10x10 pixels in size.
transparent background is best
draw a one pixel line along the very bottom, and along the very right.
goto edit ->define pattern

then goto whatever you want to fill... goto edit, and goes "Use" select Pattern... and select the pattern you just made.

And of course play with the size of the original image, and the pixel width of your lines, etc. etc. Hopefully that works for you.