Next youll want to consider what theme or style you want your portfolio to have. This will depend upon your audience. For a job taking portraits, you should only include your portrait work. You could have a collection of black and white or sepia work, a set of shots taken with a specific camera format or a collection of shots from a specific time period or geographical region.
If you are looking to mix up types and styles of shots, make sure you have a valid reason for doing so. Remember that regardless of the theme, you should ensure a consistent colour balance and quality throughout the set of work.