@Smart Teen,
As someone who had his home turned into a highschool refuge camp for 4 years I can tell you that my mom always commented on which of my friends were good guests.
Criteria she used
1: They were eating enough
2: If they had decent table manners
3: Had something insightful to say on either the parsha or just something going on in the world
4: Decent sense of humor
5: Polite in their table manners and their dialouge with other guests. (some of my friends had very different views on life and it could get ugly if not defused)
6: It wasnt imperitive but that they bring something (something practicle rather than ostentatious)
Most importantly!
7: If they called after shabbous and said thank you!!