Preparing a photo before you print it is helpful. Consider your canvas's proportions, and crop it digitally (another convenience of computers) according to those proportions. Then check to see whether the image looks dull - does it need more contrast? Rather than increasing the contrast, adjust the levels in your photo program (it may be called "adjust colors"). I'll show how in tomorrow's workshop for those who are taking it.
Next, print on photo or brochure paper to maximize the range of colors you can print. It does help!