I learned this easy way to make the diamond pattern on purses a few years ago from a booklet that has since been lost. I have looked and looked for the book, but its just not going to turn up!
This method will work for projects where the back will be hidden. For example, the lining in a purse or tote would cover the lines you draw. Just don't use a thin lining fabric that the lines would show through.
You make a quilt sandwich, with your outer fabric, quilt batting and the back fabric and pin baste. The back fabric can be any fabric you have on hand because it will not be seen after you finish the project. It does need to be light enough for your drawn lines to show up well.
Then using a ruler, draw the lines on the back. I used a black pen.
Then sew your lines from the back of your pieces starting in the middle and working your way out.
You could just as easily mark the front of your project with a regular quilt marking pen,but with the lines on the back, you don't have to worry about removing the marks.
Here are two tote bag panels ready to put together. The lines on this project are 2 inches apart, but one inch lines would be very nice too!
I forgot to take a picture of the finished project, but the bag is an Alabama University bag for my son's girlfriend.