I usually plan every part of a trip in detail, but for whatever reason decided to not plan our day in the historic part of Philadelphia.
We opted just to go to the visitor center and ask them for tips. The lady and guy who helped us were fantastic. They busted out a map, circled and described the best attractions to see with our time in a logical walking order. They gave us tips to avoid liberty ball crowds, and even tips on where to get Philly cheese steaks (cliche, we know).
Instead of planning out each step of a visit, just let them do the work! I think you need to come here for tickets for independence hall anyways.