Review portfolio requirements. Each school has specific guidelines governing their portfolio submission process. These are found on the school's admission website or you can call a school representative for more detailed information.
Most art colleges generally have requirements based on the kind of program the applicant is applying to. For example, the Art Center College of Design requires applicants to their illustration program to submit a combination of 10 to 15 landscapes, portraits and sketches. Heeding the school's stated requirements on the front end will spare you the embarrassment of having an inadequately prepared portfolio presented for review.
Select your best pieces for the portfolio. Avoid the "kitchen sink method" where you simply add anything and everything you've done that is halfway good. Each piece must showcase the skills you have learned thus far. Also, keep the relevance of your selections in mind. If you are going for acceptance into an illustration program, then you want to include pencil drawings and some paintings, not photographs even though you may be a great photographer.
Buy a portfolio case. Heavy stock portfolios made from recycled materials are economical and useful for getting your work to and from class. But, when meeting with an art school admissions representative or applying for a job, your best bet is a standard black soft case portfolio. Spending more on a nicer portfolio model provides a more professional look to your work. The most common dimensions are 17 by 22 by 3 inches which will accommodate larger illustrations and paintings. However if you work exclusively with smaller dimensions (graphic design or photography), choose a portfolio that is a better fit.
Take digital photographs of your artwork. If you will not present your portfolio in person, you will have to create slides or post the pieces on the internet. The first step to either task is taking pictures of your artwork. Digital cameras are best because of picture quality and ease of editing.
Order color slides. Almost any one hour photo shop can perform this service as well as some online companies. Simply send in your digital images, and they will convert them to color slides. Order one set for every school you're sending your work to plus one master set for yourself. Send the slides to your preferred school's admissions office.
Submit your portfolio in digital form. Some schools want your portfolio on a CD. Others, like the Pratt Institute in New York, have an online system that allows you to submit digital photos of your work over the web.