A couple of things I learned from my trips to Poland:
Write down as much as you can. It's an incredibly powerful and inspiring trip, but the inescapable reality is that inspiration fades. Down the line, your notes will serve as a reminder to the intensity of the emotion and connection you felt over the trip.
Try to take most of your notes AFTER each stop, rather than during. Let yourself be fully present at each place, listening to the group leader as he describes each stop. Afterwards, write down what you remember. You'll get down less information, but you'll have let it hit you that much more strongly.
Hundreds of history books have been written, detailing the facts and stories about each city and community. Your goal in writing notes is not to add another book to the shelf! Make sure to write about feelings and reflections as part of your notes, flowing from the facts that inspired or led to them. Looking back in a few months, you'll want to remember both what you saw, as well as how that made you feel.
Use bus time well. There are many ways to do that - you can journal, think, discuss something meaningful and relevant with whoever's sitting next to you, learn a little Torah (V'Hagisa Bo Yomam VaLayla applies everywhere, including Poland), or catch up on sleep to be ready for the next stop. If you need to give yourself space to process or decompress after a particularly difficult stop, music could be useful. Don't just waste the hours on the bus sitting mindlessly on your phone!
The trip is packed, with early wakeups and late finishes on many of the days. Do as much as you can to maximize sleep at night - talk with friends on the bus, not at night! And obviously, avoid losing sleep due to your phones (if you brought them at all).
The trip itself is often pre-empted with a shiur or two on different approaches to dealing with Emuna and the Holocaust. It's incredibly difficult to come to the grips with the thought that a God who loves and cares for us could turn His back on us and allow the Holocaust to happen. The shiurim often present different approaches to deal with the question. Even so, it is wholly normal to be bothered by this question over the trip itself. Don't feel like you're wasting anyone's time by bringing up the question with a friend or staff member on the trip. It's worth exploring your feelings on the subject and talking out how your relationship with Hashem is evolving due to the trip.
You'll experience a wide range of emotions over the course of the trip. In one day, you can easily feel like crying, screaming in anger, laughing, and lashing out - sometimes all at once! It can be a draining and confusing experience. Try to identify what you're feeling and where it's coming from. Don't think that you need to feel sad the entire time, or match whatever emotion the person next to you is displaying. Everyone has their own ways of processing experiences; what's important is to be aware of an experience's impact on you, not to make sure that you "did it right." You very well might not be the crying type, instead being more prone to appreciating the sparks of light at each stop, or feeling consumed by anger (at the Nazis, at Hashem, even at the Jews - all possible targets). At the same time, it can be enlightening to discuss your feelings with friends and hear their perspectives, sometimes giving you a different angle from which to see a story.
Try to be mindful of how your friends are dealing with different parts of the trip. For someone having a hard time, it can mean a lot for you to approach them and just ask how they're doing and if they want to talk. Having a listening ear available as an outlet for their emotions is a powerful way to process what's happening inside their heads. Also, try to be respectful of their experiences. For example, imagine the group returns to the bus after a particularly difficult stop. Some people are prone to quickly losing their serious, "sad faces" and go back to lightly joking around; that may even be their defense mechanism against such strong emotions. Others, though, want to sit with the pain and let it percolate, allowing it to stew as they think it through. It is often disturbing to the second type of person to see their friends so easily shrug off the pain and move on as if they weren't just two minutes removed from a concentration camp or destroyed shul. Try to recognize that and give them some space.
The trip is powerful and inspiring. You'll feel as if you'll never look at your life in the same way again - the things you used to take for granted, you now recognize as incredible Chasadim. You may also have a better understanding of the trauma your grandparents lived through and are often still struggling with. You may have been inspired by the courage of the Warsaw Ghetto Uprising, who resolved to show the Nazis that Jews will no longer walk as sheep to slaughter. The world-changing impact of the State of Israel and the IDF takes on new meaning when you see that a single bomb on the tracks to Auschwitz could have saved hundreds of thousands of lives. You might also have a different perspective on our relationship with America after learning more about what they did, and what more could have been done, during the War.
With all these thoughts and more, you might feel like you'll never live your life the same as you did before the trip. There is only one way to make that happen: Take on one new "Minhag," one practice to remind you of what you're feeling now. This will solidify what you're feeling, and create something tangible to remind you of it in the future. For example, if you want to continue appreciating the things you used to take for granted, choose something specific to focus on each week and thank Hashem for. One week could be different articles of clothing, another week the amount and variety of food you eat, another week different family members...Translating your feelings into action will keep them alive and yield a real, long-lasting impact from the trip.