If you're looking for a meeting place or a good stop around ½ or halfway between Guilford and Pittsburgh, you can try Hazleton, PA, which is about 3½ hours west of Guilford, or about 4 hours east of Pittsburgh.
Another possible place to stop near the midpoint is Bloomsburg.
About ¼ or a fourth of the way, you can stop at Newark, NJ. This is almost 2 hours southwest of Guilford.
About ⅓ or a third of the way, you can stop at Hopatcong, NJ. This is a little over 2 hours west of Guilford.
About ⅔ or two thirds of the way, you can stop at State College, PA. This is about 5 hours west of Guilford, or about 2½ hours east of Pittsburgh.
About ¾ or three fourths of the way, you can stop at Altoona, PA. This is about 5½ hours west of Guilford, or about 2 hours east of Pittsburgh.
If you drive straight through without stopping at all, the total distance is 460 miles. The distances shown above don't include local roads to get into each town, so if you're planning a long road trip, make sure you factor in traffic and road conditions, rest stop breaks, and interesting detours along the way. If you're in a rush, you can do the trip with zero stops, and your total travel time would be around 7 hours, 22 minutes.