My part-time job

I work at the Daiwa Roinet Hotel as a reception staff. I carry dishes and drinks in it. There are a lot of leftover food especially after buffet style party. I think the reason is that buffet style dish doesn't be settled for each customers,so they become tired of taking food at many times. Do you have any ideas to reduse leftover food? Sometimes we can eat it,but it is  too much for us to finish !!