If you are driving to Gettysburg, consider hiring a licensed guide (you can do this at the Visitor Center). They will drive your car and take you to key places while they narrate, freeing you to listen to their knowledgeable interpretation and pay attention to the sights. Some places you'll view from the car, others you'll get out and walk around.
It's heartbreaking to stand at the treeline where the Confederate troops staged for their final assault and stare across the vast open fields they had to cross before trying to charge uphill against dug-in Union positions and their cannon.