We have just been to a function where it was bring a plate. I made some slices and just put a bit of each on the plate. When it was time to go there was only a couple of pieces left as they were tipped onto another plate and I took home a clean plate. I know the salads that were leftover the owners took them home also. I have noticed that if you make a salad and its in your bowl you will bring home the leftovers.
I have learnt over the years never to leave the bowl/plate behind as it sometimes takes forever to get it back, then find you need it the next week.