The thing I am most proud of in my PLTW career is all of the friendships and connection I have made throughout my last four years in the program at Samo, which has made all of the group work immeasurably easier to work on.
The advice I would give to an incoming freshman would be to befriend as many people in the class as you can, as they're going to be in your life for the next four years, and hopefully beyond that. Also, learn from my mistake and ask for help if you need it.