CC-BY / Benjamin Franklin Institute of Technology
CC-BY / Robert & Pat Rogers
Where will you celebrate? Any place, from home to a corner of a café, is a great place to celebrate. If you have enough space and energy to clean after the event, your home is perfect to host your guests. On the other hand, many cafés and coffee shops are quite open to the idea of giving you a corner of their space for you to celebrate. It's nice, but not as private as your home, of course.
When will you celebrate? As soon as possible. After graduation, everything is a roller coaster. You and your friends will be moving to the next chapter of your life, traveling away or starting something new, so people will all be very busy. That's why your event should either take place an hour after your school's graduation or as soon as the next day.
Who will be invited? Everyone who took part in your life up to this very important moment. People who helped you through your years until graduation and friends who shared with you priceless and memorable moments must definitely be on the list.
How to make it memorable? Make sure you wear your graduation gown and put a graduation hat on your cake. Play high school pictures and videos on a big screen. Put many balloons at the entrance, it will look good and it can be used as a background for pictures. Take many selfies with different people so you can all put them in one frame later on. You can also ask people to write you something on a paper that you will shape as a diploma and keep as a souvenir.