Guys, there are no hard and fast rules as to what goes in your portfolio. Just a simple guideline: include your very best work that you are most proud of and that shows all your skills. That's it.
I was asked, for the third time, about whether a book can have more than one PSA piece in it. Each of the students who asked me was genuinely surprised to hear me say that there are no actual limits on what type of work to include in a book. Put in your best work, period.
I won't think poorly of you if you have 3 or even 4 PSA pieces. I won't complain if you only have 2 pieces in a campaign vs. the standard 3 (why 3? I always wonder). Nobody sat down and outlined the makings of student portfolios. Don't feel like there is a content outline you have to follow.
I want to see that you can think. I want to see that you can translate a creative concept to a creative layout. I want to see that you can execute on your skills (be you a writer or an art director). Beyond that, I don't really care too much about what the ad is for. Although, I will caveat these thoughts with the obvious, "in my opinion." Some recruiters may feel differently. They may want to see no less that 3 pieces to a campaign or think that one PSA is quite enough.
But one thing I am sure we would all agree on: we only want to see work you feel is your absolute best.