Travel! The best part of abroad is visiting other cities and experiencing new cultures. During my abroad experience I traveled to: Dublin, Paris, Brussels, Copenhagen, Geneva, Interlaken, Tel-Aviv, Jerusalem, Rome, Lisbon, Florence, and the Amalfi Coast.
My favorite cities: Interlaken (do Bus2Alps: it organizes everything for you- transportation, skiing, paragliding, sledding, etc.), Tel-Aviv, Amalfi Coast
Bring 2 big duffels and a carry-on bag, which you will use for traveling. Make sure your carry-on is in accordance with the European airline size requirements. Ryanair and Easy Jet (inexpensive airlines) have strict baggage requirements. You will have to pay an absurd amount of money if your bag is even slightly bigger than what is required. Check the airline websites for specific measurements.
The Eurostar is very easy to get to Paris and Brussels. Make sure to book in advance for cheaper fares. Train time is approx. 2 hours. Trains leave from King's Cross St. Pancras tube station.
I flew mostly Ryanair and Easy Jet. They are inexpensive airlines, but definitely book in advance for cheaper fares. I recommend over school breaks, traveling to more than one city, it is cheaper to fly from city to city because all flights are booked as 1-way tickets. It is not cheaper to book round-trip.