Step 1: Get Materials
Keep in mind what you may plan to shoot pictures of, for it will be a good factor in deciding how big you want your box to be. Since were laying poster board in the box, I would recommend that you keep the boxes' dimensions within the width of the poster board. The two colors of poster board I would recommend getting are white and black, but of course its also good to experiment and I find that blue and red also make good backgrounds. But, use any colors you wish. The color of the poster board sets the "mood" for the picture i.e. black background would be for like sleek watches or high dollar items, where as white may be for something like a vase with flowers, or something "light" and "airy"