Snacks. Snacks are important. In Emotional Design by Don Norman, a study by Alice Isen (et al) is mentioned. The results of the study say that people think “outside of the box” better when they have just received a small gift. Nothing bg, just something that makes them feel good.
Food is huge in our office – especially things that are not daily things. Provide cupcakes or a box of chocolates or some pie or whatever.
Good luck.