Farewell parties, just like any other party, should have a lot of interactive stuff for the guests. Your choice of activities should depend on the kind of people you are throwing the farewell party for. For example, a farewell party for high school graduates should have different activities than that for university graduates.
However certain things are common to all parties and should be taken good care of, no matter who the party is for:
1. You should make sure the venue is appropriate for the kind of party you are throwing. It should have enough space, light etc and should be easily accessible.
2. Music: Good music is necessary for any party. A party just is not a party without quality music. Make sure the music you choose is something that everybody is going to enjoy. It is preferable that the music should have a danceable beat.
3. The second most important thing, or maybe even the first most important thing, is food. Make sure there is enough food for everyone. And it is something that is enjoyed by everyone.
4. Interactive Games. You should have games for your guests. These can vary according to the ages and interest of your guests. For example, you can have singing competitions, food competitions. Etc.
I hope you throw a wonderful party and enjoy it :)