Select the ones that show them what you look like, not how much photoshop was put into it, any that have been published (in a meaningful way) and a simple headshot/body shot you're willing to leave with them.
Avoid taking any with the photographers logo stamped on it. Only has comedy value to agencies.
Re your portfolio, I would suggest a selection to show various styles, levels and abilties. Though you may get a feel from the interview that they are after something specifc. Have some justification as to why you have picked a certain image, it may show an aspect of your personality, this was my first time doing this, it was a unqiue image due to... etc etc.
Remember your attitude etc will be key to it all too.