Take high quality digital photos. Shooting in sunlight is ideal. You don't need special lights. Make sure the photo captures the full piece. For very detailed or intricate work, a close up is useful, too.
Edit the work in the photo editor. With a good shot, few adjustments are typically needed. Crop the photo to the work's dimensions. Adjust the levels to make the work bright, but don't overdo it so the image is bleached. Contrast can bring out details. The sharpening tool makes the image crisp.
Print out your photos on photo paper. Use a full sheet (around 8 inches by 11 inches). A big image is desired for clarity. Allow a few minutes to dry the photos after printing.
Insert the photos into the sheet protectors. If the portfolio has sheet protectors, use those. Get the nicest portfolio or notebook you can. It's part of a professional presentation.
Print out a resume for yourself. Include contact information. You can also do a simple statement. This should describe your work without jargon. Place the documents in the back of the portfolio. If you can, burn a CD-ROM with digital versions of your portfolio images. You can leave this should the person who reviews the portfolio be interested.