Obviously you won't want to work on your original photograph. You can photocopy or scan and print your picture. If using a computer, you can use your photo or paint program to add your grid before printing. Most programs will have a 'grids and rulers' option you can use as a guide. If you only have an original photograph and no access to a scanner, you can also use a sheet of plastic - clear photocopy sheets are the best, or a clear sleeve from a display book; even a sheet of glass or perspex from an old picture frame - and draw your lines on that instead of your photo.
Copy the grid onto your drawing paper, using a sharp, B pencil (medium hardness) and a light touch, so that you can erase it easily. Although you can use this process to scale a drawing up or down, it's much easier to get good results if you use the same sized grid.