It totally depends if you are 1st time visitor or not. In case you plan to explore 1st time i would suggest you to include following:
Humayun tomb in morning CP during day time
Hauz khas village near evening time. Youcan end you day with dinner at social in hauz khas village. In case you have already been to these places I highly suggest you to take a day trip to lohagarh farm if you are in a group. It has amazing activities like camel ride,board games etc and good food along with DJ. You will have fun.