A portfolio is a collect of work you wish to showcase. Your portfolio should show clients what you can do, down to what you specialize in and other talents. Knowing what to put in your portfolio can be hard.
I read this post on another blog, and Liked a few of the points they said. http://www.creativebloq.com/portfolios/improve-your-portfolio-1233214
All killer, no filler
This is short and simple, the longer someone has to take to find information about you the more likely they will leave.
All around experience
All experience matters not just experience in the design field, employers take this into consideration.
This shows employers that you are motivated to get out and get things done on your own.
After reading those were the big things I took away from it. I will keep these in mind as I continue to expand my portfolio!