You cannot visit Pittsburgh without going to the Strip. Check out all the cultural markets and Pittsburgh merch on Penn Ave or the brand new Terminal shops on Smallman Street. Highlights are Wholey's, Mancini's, Jimmy and Nino's (for pepperoni rolls), and, most importantly, Primanti Bros! Saint Stanislaus Kostka and Saint Patrick Catholic Churches are great stops too.
The North Shore is the best place to go to walk around, get a bite to eat, and enjoy a great view of the city. Smushed between PNC Park and Heinz Field, there are a ton of great restaurants and bars in this vibrant district with plenty of outdoor seating.