Select several finished prints or high-quality photographs of your work. There should be no more than 20, as it should be practical for you to walk somebody through your entire portfolio within a single meeting.
Decide on your portfolio's focus and narrative. There should be a clear chronology and message within the selection of work you include, as this will prevent it from seeming disorganized or disjointed.
Ask for a trusted authority to review your portfolio after you complete it; he may have advice and suggestions that could prove beneficial.
Purchase a portfolio display book. This should be large enough to give the viewer a good grasp of your work, although you may need to digitally shrink your images to make them fit.