All portfolios include images of your work. The first step in making any type of portfolio is to gather your best images of your work. It helps if as you work you make a point of taking photos of projects as you go along, but even if you have not you may be able to still lay hands on your work and photograph it now.
If you are making a Traditional portfolio that you can carry around with you, you can often include originals of your work if your work primarily is 2 dimensional artwork, plans, technical drawings, or similar items so long as they fit into the portfolio size you have chosen. If however, you do work that is too large, ephemeral or three dimensional for fitting into a traditional portfolio, you will want to photograph your objects (food, sculpture, paintings, murals, furniture, dental implants, makeup, plants, etc) and print them to the correct size for your portfolio.
If you are making a Slideshow Portfolio, Web-based Portfolio or PDF Portfolio you will want to photograph (or scan) everything, including your 2D artwork for insertion into your slideshow, web site or PDF.
If you are making a Video Portfolio you need to gather your video clips, animations etc, or film those other objects (robots, performance art, sculpture, horticulture, jewelry etc) in video or 2D format so you have images to insert into your video.
If you have a smartphone you typically have an adequate camera for doing all of this, but you may have found your photos are still not coming out the way you would like them to. Because you are photographing objects, and likely wish to show detail, you may need to move the object to a place where you can get bright but diffused lighting to show maximum detail. If you have been blessed with a very foggy day you can simply take your object outside, but if not you may want to find a building where there is lots of bland indoor neon bulbs and some gray industrial carpeting or a cement floor or wall for background. If however you live in a tiny dark ground floor apartment, laying a bed sheet over the fence around your tiny "garden patio" slab of concrete on a too- bright day will diffuse the sunlight coming in which will also work. If your situation leaves you where you must take your photos indoors using assorted lamps for light, bring the lamps closer, and make sure to clip a piece of paper or cloth with a clothespin between any bare bright bulb and your object:
If your objects are small and/or shiny (jewelry, machine parts, dentures, shiny ceramics) you may want to buy or make a light box to get best results. Small and shiny objects are very difficult to photograph well without doing this, so it is worth your time learning how you make in the video at left.
As you can see, while this setup used $10 of materials, many of the purchased items (cardboard box, tape, snap knife, lights, sheer white cloth or paper) can be found around your home. For anything small or shiny you can also find LOTS of good how to information for photographing this stuff from eBay sellers sharing tips on "How to Photograph Jewelry" (Links to an external site.) as this is the smallest and shiniest of things to photograph, and thousands of them are out there doing it daily worldwide. If English is your second language, and you wish you could get your tutorial on this in Chinese, Spanish, Hindi, etc. you can, just search for it.
If you are photographing 2D art for your portfolio there are also a lot of good tutorials like this one at left. Again, you want bright but diffused/indirect light.
If you no longer have your work (somebody ate it, bought it, you gave it away, etc) and you only have crummy pictures on your phone to show for it, you will be pleased to know there are tutorials to help with that too in Fixing bad photos.
Gather or create images, and fix any that need help, and decide which of your pictures you wish to feature.